add table route core functionality

[3AceShowHand]

Implement the core table route functionality for TiCDC changefeeds:

• Match table route rules and map source schema/table names to target names.
• Apply routed names to table metadata and DDL events.
• Rewrite parser-supported DDL SQL so referenced table names stay consistent with routed metadata.
• Add tests based on real DDL events generated by EventTestHelper, including cross-database and multi-table DDL cases.
• Explicitly reject parser-unsupported index DDLs until parser-backed support is available.