feat(jdbc): arrow format support decimal.

[youngsofun]

Summary

This PR updates JDBC Arrow negotiation to match the server-side protocol introduced in databend#19780.

Arrow is now enabled only when login reports server_max_arrow_result_version >= 3. When Arrow is used, the driver sends:

• arrow_result_version_max=3
• arrow_features.decimal64=false

This removes the old fallback that inferred Arrow support from the server version and allows Decimal-related Arrow integration tests to run again.

Changes

• Require server_max_arrow_result_version >= 3 before enabling Arrow transport.
• Remove the old server-version-based Arrow capability fallback.
• Extend query requests with arrow_features.decimal64=false in Arrow mode.
• Omit Arrow-only request fields in JSON mode.
• Update unit tests to cover:
  • Arrow enabled when server advertises result version 3
  • Fallback to JSON when server advertises result version 2
• Re-enable Decimal-related integration tests in Arrow mode.