Add dedicated JDBC regression tests for hasOverlappingSiblings overlap detection

[harshitaajoshi]

What

Adds comprehensive regression test coverage for hasOverlappingSiblings in the JDBC persistence layer, as requested in #4600. Also adds a concrete H2-based parameterized test runner so these tests can run locally without Docker.

Why

The existing JDBC test only covered a basic parent/child overlap and a non-overlapping case. The NoSQL layer had much broader coverage for edge cases (trailing slashes, both overlap directions, duplicates, entity drops) but the JDBC layer did not. These regression tests ensure the JDBC overlap detection behaves correctly across all important scenarios and prevents future regressions.

Fixes #4600

Changes

• Added 4 new test methods to AtomicMetastoreManagerWithJdbcBasePersistenceImplTest:
  • testHasOverlappingSiblingsTrailingSlashVariants: verifies that a location without a trailing slash still overlaps with a stored location that has one
  • testHasOverlappingSiblingsParentChildBothDirections: verifies overlap is detected when the candidate is a child of an existing entity AND when it is a parent of an existing entity
  • testHasOverlappingSiblingsDuplicateLocations: verifies that an exact duplicate base location is reported as overlapping
  • testHasOverlappingSiblingsAfterEntityDrop: verifies overlap persists while duplicates remain, and disappears only after all overlapping entities are dropped
• Added a createOverlapTestCatalog helper to reduce boilerplate across new tests
• Created AtomicMetastoreManagerWithJdbcBasePersistenceImplH2SchemaTest as a concrete H2 parameterized test runner (mirrors the Postgres IT pattern but runs without Docker)

Checklist

• Don't disclose security issues! (contact security@apache.org)
• Clearly explained why the changes are needed, or linked related issues: Fixes JDBC: Add dedicated regression coverage for hasOverlappingSiblings behavior #4600
• Added/updated tests with good coverage (and explained how)
• Added comments for complex logic
• Updated CHANGELOG.md (if needed)
• Updated documentation in site/content/in-dev/unreleased (if needed)