executor: avoid sum from avg overflow (#30010)

[ti-srebot]

cherry-pick #30010 to release-4.0
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/30383

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git push git@github.com:ti-srebot/tidb.git pr/30383:release-4.0-9aa756336e7b

---

What problem does this PR solve?

Issue Number: close #29952

Problem Summary:

1. the sum from avg may overflow, we should infer the type as the normal sum.
2. the previous PR expression, planner: fix decimal results for aggregate functions #20017 is a hack to fix the issue , we should let the final agg output the target return type which is inferred in TypeInfe() for Agg.
3. typeInfer4xxx should valid the precision and scale of decimal type.

What is changed and how it works?

Check List

Tests

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

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

None

[ti-chi-bot]

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[ti-chi-bot]

@ti-srebot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[xhebox]

close for DMR version