Staggered merges metrics

[Sukriti0717]

Implemented a comprehensive metrics framework that captures 8 key metrics across scheduler and shard-level operations:

1. Total scheduler execution time
2. Total Merges Triggered
3. Total Merges Skipped
4. Skips count due to Node Validator
5. Total failed force merges
6. Shard specific
   1. Time taken by force merge
   2. Shard size
   3. Segment count

[github-actions]

❌ Gradle check result for b8527b9: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?