feature: upgrade Netty to 4.2.15.Final

[xjlgod]

• I have read the CONTRIBUTING.md guidelines.
• I have registered the PR changes.

Ⅰ. Describe what this PR did

• Upgrade Netty from 4.1.137.Final to 4.2.15.Final through the Netty BOM.
• Migrate Seata transport event loops from deprecated Netty 4.1 APIs to the Netty 4.2 IoHandler / MultiThreadIoEventLoopGroup APIs.
• Keep the allocator explicitly configured as pooled, and remove use of Netty internal APIs.
• Ensure Seata's Netty BOM takes precedence over Spring Boot dependency management in server-related modules.
• Align related gRPC/Protobuf dependency management and add required direct Netty dependencies for the SkyWalking plugin.
• Update the gRPC interceptor test to use an actual grpc-netty TCP server and client.
• Add Chinese and English change-log entries under changes/.

Ⅱ. Does this pull request fix one issue?

No.

Ⅲ. Why don't you add test cases (unit test/integration test)?

N/A. This PR updates existing tests and executes the relevant test suites.

In particular, GrpcTest was migrated from the in-process transport to a real grpc-netty TCP transport, so the test now verifies the Netty-based gRPC request path. Existing core remoting, HTTP/2, Etcd registry, and version-compatibility tests were also executed.

Ⅳ. Describe how to verify it

1. Run the relevant unit tests on JDK 8:

   • Core Netty remoting, HTTP/2 handler, channel event, and Netty client bootstrap tests.
   • Etcd registry tests.
   • extensions/rpc/seata-grpc interceptor tests.

2. Run the cross-version compatibility tests on JDK 21:

   • Verify client/server combinations across the old and new versions.

3. Build the release distribution with JDK 25 and the release-seata profile.

4. Inspect the generated server and naming-server distributions:

   • All bundled Netty artifacts must resolve to 4.2.15.Final.
   • No netty-4.1.x artifacts should remain.
   • Startup scripts must retain -Dio.netty.allocator.type=pooled.

Ⅴ. Special notes for reviews

• Netty 4.2 is not intended to coexist with Netty 4.1 in the same runtime classpath. This PR centralizes version resolution through the Netty BOM and overrides Spring Boot-managed Netty versions where necessary.
• The migration is intentionally scoped to deprecated event-loop APIs and direct internal-API usage; business protocol behavior is unchanged.
• The SkyWalking plugin now declares direct provided Netty dependencies because it directly uses Netty Channel and AttributeMap types.

[codecov]

Codecov Report

❌ Patch coverage is 88.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.38%. Comparing base (41694e1) to head (94ece23).

Files with missing lines	Patch %	Lines
...che/seata/core/rpc/netty/NettyClientBootstrap.java	66.66%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                2.x    #8209      +/-   ##
============================================
+ Coverage     73.22%   73.38%   +0.15%     
- Complexity     1146     1147       +1     
============================================
  Files          1153     1153              
  Lines         42348    42359      +11     
  Branches       5061     5061              
============================================
+ Hits          31011    31085      +74     
+ Misses         8852     8803      -49     
+ Partials       2485     2471      -14     

Files with missing lines	Coverage Δ
...g/apache/seata/config/etcd3/EtcdConfiguration.java	46.44% <100.00%> (ø)
...che/seata/core/protocol/detector/HttpDetector.java	82.50% <100.00%> (+0.92%)	⬆️
...g/apache/seata/core/rpc/netty/NettyBaseConfig.java	75.75% <100.00%> (+3.03%)	⬆️
...che/seata/core/rpc/netty/NettyServerBootstrap.java	70.87% <100.00%> (+17.26%)	⬆️
...che/seata/core/rpc/netty/NettyClientBootstrap.java	62.88% <66.66%> (+8.63%)	⬆️

... and 20 files with indirect coverage changes

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[Copilot]

Pull request overview

This pull request upgrades Seata’s Netty stack to 4.2.15.Final via a centralized BOM and migrates the transport event-loop implementation from deprecated Netty 4.1 APIs to the Netty 4.2 IoHandler / MultiThreadIoEventLoopGroup APIs. It also updates dependency management precedence (notably for Spring Boot–managed modules), adjusts distribution startup scripts to keep pooled allocator settings explicit, and refreshes/extends tests to validate the new Netty-based behavior paths.

Changes:

• Upgrade Netty to 4.2.15.Final and enforce alignment via BOM imports + Maven Enforcer convergence for io.netty:*.
• Migrate server/client event loops to MultiThreadIoEventLoopGroup + NioIoHandler / EpollIoHandler, and explicitly configure pooled allocators at runtime.
• Update tests (including gRPC interceptor tests) and distribution scripts to reflect the new transport/runtime settings.

Reviewed changes

Copilot reviewed 20 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test-suite/test-new-version/src/test/java/org/apache/seata/core/rpc/netty/v1/ProtocolV1Server.java	Updates compatibility test server to Netty 4.2 event loop group + IO handler APIs.
test-suite/test-new-version/src/test/java/org/apache/seata/core/rpc/netty/v1/ProtocolV1Client.java	Updates compatibility test client to Netty 4.2 event loop group + IO handler APIs.
test-suite/test-new-version/src/test/java/org/apache/seata/core/rpc/netty/multiversion/AbstractMultiVersionCompatibilityTest.java	Migrates multiversion test event loops to Netty 4.2 IO handler model.
server/pom.xml	Imports Netty BOM ahead of other BOMs to ensure Netty version precedence.
namingserver/pom.xml	Imports Netty BOM ahead of Spring Boot BOM to avoid Netty version drift.
mock-server/pom.xml	Imports Netty BOM ahead of Spring Boot BOM to keep Netty aligned.
extensions/rpc/seata-grpc/src/test/java/org/apache/seata/integration/grpc/interceptor/GrpcTest.java	Moves interceptor test to real grpc-netty TCP transport and JUnit Jupiter lifecycle.
extensions/apm/apm-seata-skywalking-plugin/pom.xml	Adds direct provided Netty dependencies required by the plugin’s Netty API usage.
distribution/bin/seata-setup.sh	Ensures pooled allocator system property is set in server setup script.
distribution/bin/seata-server.bat	Ensures pooled allocator system property is set in Windows server launcher.
distribution/bin/seata-namingserver.bat	Ensures pooled allocator system property is set in Windows namingserver launcher.
distribution/bin/seata-namingserver-setup.sh	Ensures pooled allocator system property is set in namingserver setup script.
dependencies/pom.xml	Adds Netty BOM import in dependency management for unified Netty 4.2 module alignment.
core/src/test/java/org/apache/seata/core/rpc/netty/NettyServerBootstrapTest.java	Adds coverage asserting server uses Netty 4.2 MultiThreadIoEventLoopGroup when epoll disabled.
core/src/test/java/org/apache/seata/core/rpc/netty/NettyClientBootstrapTest.java	Extends coverage for pooled allocator option and Netty 4.2 event loop group selection.
core/src/test/java/org/apache/seata/core/rpc/netty/ChannelEventHandlerIntegrationTest.java	Migrates integration test event loops to Netty 4.2 IO handler model.
core/src/main/java/org/apache/seata/core/rpc/netty/NettyServerBootstrap.java	Migrates server event loops to Netty 4.2 APIs and explicitly sets pooled allocators on channels.
core/src/main/java/org/apache/seata/core/rpc/netty/NettyClientBootstrap.java	Migrates client event loops to Netty 4.2 APIs and explicitly sets pooled allocator + improved epoll fallback logging.
core/src/main/java/org/apache/seata/core/rpc/netty/NettyBaseConfig.java	Simplifies epoll selection logic around Epoll.isAvailable().
core/src/main/java/org/apache/seata/core/protocol/detector/HttpDetector.java	Adds bounds check to prevent prefix scan on insufficient readable bytes.
config/seata-config-etcd3/src/main/java/org/apache/seata/config/etcd3/EtcdConfiguration.java	Removes Netty internal ConcurrentSet usage in favor of ConcurrentHashMap.newKeySet().
changes/zh-cn/2.x.md	Adds changelog entry and contributor acknowledgement for the Netty upgrade.
changes/en-us/2.x.md	Adds changelog entry and contributor acknowledgement for the Netty upgrade.
build/pom.xml	Defines netty.version=4.2.15.Final, upgrades enforcer plugin, and enforces Netty dependency convergence.

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[WangzJi]

Could you confirm whether seata-console also needs to be aligned with Netty 4.2.15? Under the source-release profile, its effective dependency tree still resolves io.netty:* to 4.2.12.Final via Spring Boot 4.0.6. If only the final server/namingserver distributions need alignment and they already resolve to 4.2.15, no change is needed; otherwise, console should import the Netty BOM before Spring Boot as well.

[Copilot]

Pull request overview

Copilot reviewed 20 out of 24 changed files in this pull request and generated 1 comment.