[fix](fe)eliminate noop cast in thrift by overriding treeToThriftHelper

[starocean999]

master is ok, this bug only exists in 4.1 and 4.0

Issue Number: close #xxx

Related PR: #39670

Problem Summary:
CastExpr's treeToThriftHelper function eliminate noop cast, but there is another override version shoud be handled.

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[starocean999]

run buildall

[morrySnow]

add ut, test case and add intro pr number in description

[morrySnow]

this override should be removed

[starocean999]

run buildall

[freemandealer]

/review

[hello-stephen]

FE Regression Coverage Report

Increment line coverage 100.00% (2/2) 🎉
Increment coverage report
Complete coverage report

[github-actions]

Automated review completed for head 34d26c8ad899d7e2dfe500a2ffce5114ea2bd96e.

• Correctness: the visitor-aware override is the correct dispatch point for both root and nested thrift serialization. Eliding a no-op cast preserves flattened child arity and forwards visitor-specific normalization to the child.
• Tests: the new CHAR(6) -> TEXT regression is non-vacuous and would fail on the parent implementation; the INT -> TEXT control verifies that a real cast remains serialized.
• Compatibility, lifecycle, performance, and security: no issue found. The change adds no mutable state, I/O, concurrency, or external-interface surface, and query-cache slot/function normalization remains intact.
• Existing review context: the earlier request to remove the redundant one-argument override is addressed in the current head.
• User focus: no additional focus was provided; the full PR was reviewed.
• Validation: the live PR head/base match the authoritative bundle, git diff --check is clean, and the live compile, FE UT, CheckStyle, coverage, dependency-review, and regression checks are green. No local build was run, per the review workflow.

Conclusion: no blocking issue found and no new inline comment is needed.

[github-actions]

PR approved by anyone and no changes requested.

[github-actions]

PR approved by at least one committer and no changes requested.