[core] Support custom table paths in JdbcCatalog

[tub]

Summary

• Enable users to specify custom storage locations for individual tables in JdbcCatalog via CoreOptions.PATH, replicating the pattern already used by HiveCatalog
• The catalog-level warehouse becomes a default, but individual tables can live at arbitrary paths persisted in paimon_table_properties
• Custom-path tables behave as external tables: drop skips filesystem deletion, rename skips filesystem move

Test plan

• testCreateTableWithCustomPath — schema at custom location, getTableLocation() returns it, path stored in JDBC
• testCreateTableWithCustomPathSyncDisabled — path stored even when syncTableProperties=false
• testDropTableWithCustomPath — JDBC cleaned up, data NOT deleted
• testDropTableWithDefaultPath — data IS deleted (existing behavior preserved)
• testRenameTableWithCustomPath — metadata updated, path preserved, no filesystem rename
• testAlterTableWithCustomPath — path preserved after alter
• testLoadTableSchemaWithCustomPath — schema loads from custom location
• testGetTableLocationFallback — getTableLocation() returns default when no stored path
• All 59 JdbcCatalogTest tests pass (including inherited CatalogTestBase tests)

🤖 Generated with Claude Code

[tub]

@nickdelnano I built this on top of your table properties change. It'll allow folks to have a fully fledged catalog spanning multiple warehouses/buckets etc.

[JingsongLi]

Well-documented PR with comprehensive test plan. Supporting custom table paths in JdbcCatalog aligns with HiveCatalog behavior.

Review:

1. External table semantics: Custom-path tables treated as external (drop skips filesystem deletion, rename skips filesystem move) — correct and consistent with Hive conventions.

2. Path persistence: Stored in paimon_table_properties — the existing JDBC metadata table. No schema migration needed.

3. Fallback: getTableLocation() returns default warehouse path when no custom path stored. Backward compatible.

4. Test coverage: 9 specific tests plus all 59 inherited CatalogTestBase tests passing — excellent.

5. 388 additions across JdbcCatalog, JdbcUtils, and tests. Reasonable for the scope.

6. Edge cases to verify:

   • Custom path points to a non-existent location → create table should fail or create directory?
   • Custom path is on a different filesystem than warehouse → does FileIO resolve correctly?
   • Two tables pointing to the same custom path → should be rejected?

LGTM. Clean implementation following established patterns.