Add cleanup() to URLFilter and fix timer/client leak in JSONURLFilterWrapper

[jnioche]

Summary

• Add cleanup() lifecycle method to URLFilter, mirroring the existing ParseFilter.cleanup() pattern
• Wire cleanup through URLFilters, StatusEmitterBolt, URLFilterBolt, and all bolt subclasses via super.cleanup() calls
• Fix JSONURLFilterWrapper: the Timer and RestHighLevelClient were created inside an anonymous TimerTask with no way to cancel or close them — the timer thread runs forever and the client's connection pool is never shut down
• Store both as instance fields and override cleanup() to cancel the timer and close the client

Changes

• URLFilter: add cleanup() no-op method (matches ParseFilter)
• URLFilters: override cleanup() to iterate and call it on each filter
• StatusEmitterBolt: add cleanup() that calls urlFilters.cleanup()
• URLFilterBolt: add cleanup() that calls urlFilters.cleanup()
• 5 bolt subclasses: add super.cleanup() call so URLFilters cleanup is reached
• JSONURLFilterWrapper: store timer/client as fields, override cleanup()

Test plan

• Verify compilation with mvn compile -pl external/opensearch -am
• All core unit tests pass (mvn test -pl core)

🤖 Generated with Claude Code

[rzo1]

Needs checkstyle