br: add waitgroup for delete type files

[Leavrth]

What problem does this PR solve?

Issue Number: close #43739

Problem Summary:
no block between PUT and DELETE files restore.

What is changed and how it works?

add the block

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

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

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• 3pointer
• BornChanger

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[hawkingrei]

/test build

[hawkingrei]

/retest

[3pointer]

/merge

[ti-chi-bot]

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

Commit hash: 88a46bc

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #43796.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #43797.