dumpling: optimize dumpling log level (#29341)

[ti-srebot]

cherry-pick #29341 to release-5.3
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/29488

After apply modifications, you can push your change to this PR via:

git push [email protected]:ti-srebot/tidb.git pr/29488:release-5.3-fb5b3a0eec15

---

What problem does this PR solve?

Some dumpling's log are too frightening but they don't actually affect the dump process.

Issue Number: close #xxx

Problem Summary:

What is changed and how it works?

Revert some log level from Error -> Warn and some from Warn to Info.

Check List

Tests

• Unit test
• Integration test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lance6716
• lichunzhu

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[lichunzhu]

/merge

[ti-chi-bot]

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

Commit hash: b78d96a

[lichunzhu]

/rebuild

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@ti-srebot: Your PR was out of date, I have automatically updated it for you.

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