Summary:
**Problem:** RocksDB was making unnecessary prefetch system calls on file systems that don't support prefetch operations, potentially leading to wasted CPU cycles.
**Fix:** Add kFSPrefetch to FSSupportedOps enum to allow file systems to indicate prefetch support capability. File systems can now opt out of prefetch calls by not setting this field.
**Backwards compatibility:** File systems that don't override SupportedOps() continue to receive prefetch calls exactly as before. Only file systems that explicitly opt out by not setting kFSPrefetch will avoid the calls.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/13917
Test Plan:
- Added a new test in block_based_table_reader.
- Run existing tests: ```make prefetch_test && ./prefetch_test```
Reviewed By: anand1976
Differential Revision: D81607145
Pulled By: nmk70
fbshipit-source-id: 3bbefa05919034e8776ea4e4540cdc695cdc6d3f
3687dc4ad3