[Feature](func) Support function QUANTILE_STATE_TO/FROM_BASE64

[linrrzqqq]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

doc:apache/doris-website#3279

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. [Feature](func) Support function QUANTILE_STATE_TO/FROM_BASE64 doris-website#3279

Check List (For Reviewer who merge this PR)

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

[Thearas]

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?

[linrrzqqq]

run buildall

[hello-stephen]

BE UT Coverage Report

Increment line coverage 42.53% (37/87) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	39.15% (10403/26575)
Line Coverage	30.12% (86258/286372)
Region Coverage	27.67% (49798/179968)
Branch Coverage	24.23% (24436/100844)

[Copilot]

Pull request overview

This PR adds two new SQL functions quantile_state_to_base64 and quantile_state_from_base64 to enable serialization and deserialization of quantile state objects to/from base64-encoded strings, facilitating storage and transmission of quantile state data.

Key Changes:

• Added quantile_state_to_base64 function to convert QUANTILE_STATE objects to base64 strings
• Added quantile_state_from_base64 function to convert base64 strings back to QUANTILE_STATE objects
• Implemented comprehensive test coverage including unit tests and regression tests

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/QuantileStateToBase64.java	Frontend implementation for quantile_state_to_base64 function with PropagateNullable semantics
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/functions/scalar/QuantileStateFromBase64.java	Frontend implementation for quantile_state_from_base64 function with AlwaysNullable semantics
fe/fe-core/src/main/java/org/apache/doris/nereids/trees/expressions/visitor/ScalarFunctionVisitor.java	Added visitor methods for the new quantile state functions
fe/fe-core/src/main/java/org/apache/doris/catalog/BuiltinScalarFunctions.java	Registered the new quantile state functions in the function registry
be/src/vec/functions/function_quantile_state.cpp	Backend implementation of the serialization and deserialization logic with base64 encoding/decoding
be/test/vec/function/function_test_util.cpp	Added QuantileState type support to the function testing framework
be/test/vec/function/function_quantile_state_test.cpp	Comprehensive unit tests covering empty states, single/multi-value states, explicit states, and round-trip conversions
regression-test/suites/query_p0/sql_functions/quantile_state_functions/test_quantile_state_function.groovy	End-to-end regression tests covering NULL handling, invalid inputs, and round-trip conversions
regression-test/data/query_p0/sql_functions/quantile_state_functions/test_quantile_state_function.out	Expected output for regression tests

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[github-actions]

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

[github-actions]

PR approved by anyone and no changes requested.

[HappenLee]

LGTM

[zclllyybb]

LGTM