Add support for cancelling LocationIndex RocksDB compactions

[void-ptr974]

Motivation

Allow operators to stop an in-flight manually triggered entry-location index RocksDB compaction.

Changes

• Add a DELETE endpoint for requesting cancellation, optionally scoped with entryLocations.
• Initialize and use RocksDB CompactRangeOptions cancellation before starting CompactRange; handle RocksDB Incomplete/Aborted statuses as normal index-compaction cancellation.
• Log the request and the completed cancellation, document asynchronous GET confirmation, and add cancellation coverage.

Testing

• mvn -q -pl bookkeeper-server -Dtest=KeyValueStorageRocksDBTest,EntryLocationIndexTest,TestHttpService#testTriggerEntryLocationCompactService test
• Validated on home3 Linux.