feat: add scheduled workflow history cleaner

[youngxpepp]

Summary

Closes #1081.

Adds WorkflowHistoryCleaner, a Spring @Scheduled component that periodically deletes terminal workflows (COMPLETED/FAILED/TERMINATED/TIMED_OUT) older than the configured retention threshold.

• Pages candidates with IndexDAO#searchArchivableWorkflows and delegates the actual removal to ExecutionDAOFacade#removeWorkflow, reusing the existing execution-store / index ordering guarantees.
• Single-instance execution is enforced through the pluggable com.netflix.conductor.core.sync.Lock abstraction with non-blocking tryLock semantics — contenders exit immediately instead of queueing on the lock.
• Cooperative shutdown via LifecycleAwareComponent: any in-flight run checks isRunning() between iterations and at workflow boundaries.
• Safety rails: bounded iterations per day, fixed-size LRU of recently-processed ids (mitigates async index-delete lag), and configurable batch pauses.
• Disabled by default to keep existing deployments unaffected; opt in with conductor.workflow-history-cleanup.enabled=true.

Rolling indices (conductor_task_log_*, conductor_event_*, conductor_message_*) are out of scope — manage their retention through index-level lifecycle policies (e.g. OpenSearch ISM).

Key Properties

Property	Default	Description
conductor.workflow-history-cleanup.enabled	false	Master switch
conductor.workflow-history-cleanup.cron	0 0 * * * *	Schedule (top of the hour)
conductor.workflow-history-cleanup.zone	UTC	Cron time zone
conductor.workflow-history-cleanup.retention-days	30	Lower bound of the deletion window
conductor.workflow-history-cleanup.catch-up-days	7	Number of day-buckets walked per run
conductor.workflow-history-cleanup.max-iterations-per-day	200	Safety cap on the iteration loop
conductor.workflow-history-cleanup.processed-cache-size	5000	LRU size for recently-processed ids
conductor.workflow-history-cleanup.batch-pause	500ms	Pause between iterations
conductor.workflow-history-cleanup.index-refresh-wait	2s	Wait when the same ids keep coming back
conductor.workflow-history-cleanup.lock-id	workflow-history-cleanup	Lock identifier
conductor.workflow-history-cleanup.lock-lease-time	2h	Lock TTL
conductor.workflow-history-cleanup.workflow-index-name	(derived from index-prefix)	Override only if needed

SchedulerConfiguration thread pool size bumped from 3 to 4 to accommodate the new scheduled job.

Test plan

• ./gradlew :conductor-core:test — 18 new test cases in TestWorkflowHistoryCleaner cover lock contention, async index-delete lag, mid-run shutdown, exception handling, iteration caps, and null-result edge cases.
• ./gradlew :conductor-core:spotlessCheck
• ./gradlew :conductor-core:compileJava :conductor-core:compileTestJava
• Manual smoke test against a real Conductor deployment with OpenSearch (reviewer to validate end-to-end behavior)

🤖 Generated with Claude Code

[youngxpepp]

@akhilpathivada Could you take a look when you get a chance? This PR addresses #1081 — based on your earlier comment on the issue, I'd appreciate your review on the initial scope (global TTL only; field-value-based retention left as a follow-up).