UDF Checkpoints cleanup

[ilongin]

Implements checkpoint cleanup with TTL-based garbage collection:

• cleanup_checkpoints() method in Catalog to remove old checkpoints
• _remove_checkpoint() helper to clean checkpoint and its UDF tables
• list_checkpoints() enhancement to support time-based filtering
• get_descendant_job_ids() to find child jobs for dependency checking
• remove_checkpoint() in metastore to delete checkpoint records
• CLI integration in garbage_collect command
• Comprehensive tests for cleanup scenarios

This builds on top of the core checkpoint functionality to provide automatic cleanup of outdated checkpoints and their associated tables.

Related to #1453

Summary by Sourcery

Add TTL-based garbage collection for UDF checkpoints to prevent storage bloat while preserving dependencies.

New Features:

• Implement Catalog.cleanup_checkpoints to automatically remove outdated checkpoints and their UDF tables based on a configurable TTL with branch pruning logic.
• Add Catalog._remove_checkpoint helper to delete individual checkpoints and associated job-specific UDF tables.
• Extend metastore with get_descendant_job_ids, remove_checkpoint, and time-based list_checkpoints filters (created_before and created_after).
• Integrate checkpoint cleanup into the CLI garbage_collect command.

Tests:

• Add functional tests for default TTL cleanup, custom TTL, no-op when no old checkpoints exist, preservation of checkpoints with active descendants, partial job cleanup within a single job, full branch pruning of outdated lineages, and descendant job ID retrieval.

[ilongin]

closed as I openeed new one (it was easier to handle conflicts that way after rebasing)