util: let TypeFloat should be decoded as Float32 in Chunk (#35978)

[ti-srebot]

cherry-pick #35978 to release-6.1
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/36096

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git push git@github.com:ti-srebot/tidb.git pr/36096:release-6.1-d10d2545727a

---

What problem does this PR solve?

Issue Number: close #35910

Problem Summary:

In fieldType2Flag, both TypeFloat and TypeDouble will set datum flag as FloatFlag. However, TypeFloat will add Float32 in chunk while we directly GetFloat64 in DecodeOne function, which caused out of range error.

What is changed and how it works?

Check List

Tests

• Unit test

Release note

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Yisaer
• xhebox

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[ti-srebot]

/run-all-tests

[ti-srebot]

@Yisaer you're already a collaborator in bot's repo.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/878b5fc93f12f0c452bea4dbafeee6d3fc5ba5af

[Yisaer]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 1b3fe86