update dependencies to release-8.5

[wlwilliamx]

To ensure stability and compatibility, we must downgrade/align these dependencies to match the versions specified in the TiDB v8.5.4 release.

This alignment will require code modifications to adapt to API changes in the older dependency versions.

Affected Modules / Expected Changes:

• Update go.mod to pin TiDB, TiKV, and PD-related modules to their v8.5.4-compatible versions.
• Refactor code to adapt to API changes, particularly in:
  • TiDB parser library (package path changes).
  • PD client instantiation and API usage.
  • TiDB internal package paths (e.g., for DDL constants, session variables).
• Clean up unused dependencies that may be removed as a result of the alignment.