Optimized ConsumerOffsetManager for Faster Topic & Group Lookups

[DivyanshIITB]

This PR enhances the performance of ConsumerOffsetManager by reducing unnecessary iterations and optimizing key lookups in offset-related methods.

Key Optimizations :

1. Faster Lookups

• Replaced O(N) iterations in whichTopicByConsumer() and whichGroupByTopic() with O(1) HashMap lookups using precomputed mappings (groupToTopics & topicToGroups).

2. Efficient Cleanup Methods

• cleanOffset() and cleanOffsetByTopic() now use temporary HashSets to track keys to remove, preventing concurrent modification issues.
• Eliminated incorrect matches caused by contains() checks.

3)Optimized Offset Scanning

• scanUnsubscribedTopic() avoids unnecessary split() calls and uses bulk removal instead of modifying offsetTable inside the loop.

4)Maintains Offset-Topic Consistency

• Added updateOffsetTable() to ensure groupToTopics & topicToGroups mappings stay in sync with offsetTable.

This results in faster topic-group lookups, reduced memory overhead, and improved efficiency when managing consumer offsets.

Fixes #9240

[DivyanshIITB]

Just a gentle reminder

[lizhimins]

Need to pass all test cases first

[DivyanshIITB]

I have made the necessary changes.
@lizhimins

[lizhimins]

You can trigger the test by rebasing master.

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[github-actions]

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