log_backup: make a more rusty CallbackWaitGroup

[YuJuncen]

What is changed and how it works?

Issue Number: Close #16739

What's Changed:

This make `CallbackWaitGroup` returns an equivalent future of the `BoxFuture` returned by `wait`. Also this fixed where a stale notify may also resolve the future.

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  I ran the task for 100 times. No error happens anymore.

for i in (seq 100)
   if ! cargo test --package backup-stream --lib -- utils::test::test_wait_group --exact
       break
   end
   echo "passed $i"
end

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Release note

Fixed a bug where make there are a slight possibility that log backup lost a few records.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3pointer
• Leavrth

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[YuJuncen]

/merge

[ti-chi-bot]

@YuJuncen: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

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

Commit hash: 60c93a8

[YuJuncen]

/run-cherry-pciker

[YuJuncen]

/run-cheery-pciker

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #16755.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #16756.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #16757.