perf(RHINENG-24466): add batch-scoped caches for MQ ingestion

[rodrigonull]

Overview

This PR is being created to address RHINENG-24466.

Introduce ThreadLocalBatchCache base class and two batch-scoped caches to reduce redundant DB queries during MQ message processing:

• StalenessCache: eliminates ~3 identical Staleness SELECTs per host
• UngroupedGroupCache: eliminates 1 Group SELECT per message

Both caches are activated via context managers in _process_batch and automatically cleared at batch boundaries. Values are plain dicts (AttrDict), not ORM objects, to avoid memory accumulation.

PR Checklist

• Keep PR title short, ideally under 72 characters
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• Tests: validate optimal/expected output
• Tests: validate exceptions and failure scenarios
• Tests: edge cases
• Recovers or fails gracefully during potential resource outages (e.g. DB, Kafka)
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Secure Coding Checklist

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Summary by Sourcery

Introduce thread-local, batch-scoped caches for MQ ingestion to avoid redundant staleness and ungrouped-group database lookups within a processing batch.

New Features:

• Add a reusable ThreadLocalBatchCache base class for thread-local, batch-scoped caching.
• Add StalenessCache and UngroupedGroupCache to cache staleness configs and ungrouped host groups per org within a batch.

Enhancements:

• Wrap MQ batch processing in staleness and ungrouped-group cache contexts to reduce duplicate database queries.
• Update staleness and ungrouped-group retrieval routines to first consult the relevant batch cache before hitting the database and to store results in the cache.

Tests:

• Add unit tests verifying that StalenessCache and UngroupedGroupCache behave as context managers and prevent redundant database queries within a batch.

[github-actions]

SC Environment Impact Assessment

Overall Impact: ⚪ NONE

No SC Environment-specific impacts detected in this PR.

What was checked

This PR was automatically scanned for:

• Database migrations
• ClowdApp configuration changes
• Kessel integration changes
• AWS service integrations (S3, RDS, ElastiCache)
• Kafka topic changes
• Secrets management changes
• External dependencies