*: try check every returned err are handled (#1817)

[ti-chi-bot]

This is an automated cherry-pick of #1817

What problem does this PR solve?

close #1815

part of #1803

What is changed and how it works?

1. precheck backoff-max in source config
2. precheck do-tables, chunk-filesize in task config. (we will check all fields in another PR)
3. check an error in pkg/ha/relay.go
4. dump unit's panic issue

Check List

Tests

• Integration test

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lance6716

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[lance6716]

/merge

[ti-chi-bot]

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

Commit hash: 695a021

[ti-chi-bot]

@ti-chi-bot: Your PR was out of date, I have automatically updated it for you.

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[lance6716]

/run-all-tests

[lance6716]

/run-all-tests