backup: parallel backup and checksum to speed up backup

[3pointer]

What problem does this PR solve?

a kind of fix for #1046

What is changed and how it works?

besides pipeline backup and checksum, we can parallel them.

Check List

Tests

• Unit test
• Integration test

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release Note

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• glorv

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[ti-chi-bot]

@3pointer: PR needs rebase.

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