*: support recover relay log file with a subset of metadata (#530)

[sre-bot]

cherry-pick #530 to release-1.0

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What problem does this PR solve?

fix #443 , this should be release under v1.0.4.

What is changed and how it works?

• support recover relay log file with a subset of metadata

  • check whether the metadata is a subset of the relay log file

• also update go-mysql to fix GTIDSet.Equal.

Check List

Tests

• Unit test
• Integration test

Code changes

• Has exported variable/fields change
• Has persistent data change

Side effects

• Increased code complexity

Related changes

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

[csuzhangxc]

/run-all-tests tidb=release-3.0

[WangXiangUSTC]

LGTM

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-1.0@17a299c). Click here to learn what that means.
The diff coverage is 83.3333%.

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[lichunzhu]

LGTM