CI: drop unused sccache and handle GH workflow issues

[marxin]

Based on the discussion with @theduke, the sccache tends to be really slow and was disabled some time ago. The other changes are related to GH workflow issues reported in the VSCode.

[Copilot]

Pull request overview

This PR removes unused sccache caching infrastructure and fixes GitHub Actions workflow issues flagged by VSCode. The changes clean up workflow files by removing:

• sccache-related build matrix parameters, installation steps, and configuration
• unused target parameters from rust-toolchain actions in jobs that don't need them
• unnecessary container configuration
• cosmetic fixes to commented-out code

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
.github/workflows/build.yml	Removed all sccache-related configuration including use_sccache/use_rustcache matrix parameters, sccache installation steps, cache actions, port configuration, and unused container specification
.github/workflows/test.yaml	Removed unused target parameter from rust-toolchain action in test_integration_cli job and cleaned up commented-out WASMER_PATH exports
.github/workflows/cloudcompiler.yaml	Removed unused target parameter from rust-toolchain action in the setup job

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