Clean up code for Spark 3.5 extension

[pan3793]

Why are the changes needed?

Simple refactoring to clean up the code for the Spark 3.5 extension, e.g., remove unnecessary *Base *Helper abstraction layers, remove code for legacy Spark versions.

Note: I don't touch ForcedMaxOutputRows* because I'm going to remove it in the next PR.

Preparation for Spark 4.0 support.

How was this patch tested?

Pass GHA.

Was this patch authored or co-authored using generative AI tooling?

No.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 0.00%. Comparing base (85caea8) to head (b5a94a6).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
...ache/kyuubi/sql/zorder/OptimizeZorderCommand.scala	0.00%	4 Missing ⚠️
...a/org/apache/kyuubi/sql/zorder/ResolveZorder.scala	0.00%	2 Missing ⚠️
...he/kyuubi/sql/zorder/OptimizeZorderStatement.scala	0.00%	1 Missing ⚠️
...in/scala/org/apache/kyuubi/sql/zorder/Zorder.scala	0.00%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #6975   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files         689     693    +4     
  Lines       42637   42723   +86     
  Branches     5804    5813    +9     
======================================
- Misses      42637   42723   +86     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[wForget]

Thank you, LGTM