statistics: BinarySearchRemoveVal should use decoded val instead of encoded (#59131)

[ti-chi-bot]

This is an automated cherry-pick of #59131

What problem does this PR solve?

Issue Number: close #59130

Problem Summary:

What changed and how does it work?

The function used the wrong val as its parameter.
As a result, when the column is not string type. The function BinaryRemoveVal actually removes nothing.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

修复合并全局统计信息时，直方图构造结果可能变大的问题
Fix the issue that the global histogram might be larger than expected when merging partition table's global statistics.

[ti-chi-bot]

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@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/check_dev	b084a1a	link	true	/test check-dev
idc-jenkins-ci-tidb/build	b084a1a	link	true	/test build
idc-jenkins-ci-tidb/check_dev_2	b084a1a	link	true	/test check-dev2
idc-jenkins-ci-tidb/unit-test	b084a1a	link	true	/test unit-test
idc-jenkins-ci-tidb/mysql-test	b084a1a	link	true	/test mysql-test

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