[cdc] Support per-table configuration for MySQL database CDC

[lilei1128]

Purpose

• Add --table_conf_by_table for mysql_sync_database.
• Allow source tables to override global --table_conf table properties.
• Support per-table configuration in divided and combined modes.
• Reject per-table sink/job runtime options such as sink.parallelism.
• Document the new configuration and inheritance rules.

Tests

• Add parser unit tests for per-table configuration and duplicate keys.
• Add validation test for rejecting per-table sink configuration.
• Add MySQL CDC integration tests for divided and combined modes.
• Add coverage for per-table overrides and global configuration inheritance.