br: fix stats meta count is zero if backup has no checksum

[Leavrth]

What problem does this PR solve?

Issue Number: close #60978

Problem Summary:
the count of stats_meta is zero if backup has no checksum

What changed and how does it work?

get the count of stats_meta by collecting the files instead of total kvs of table.

Check List

Tests

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

  • I checked and no code files have been changed.

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

[tiprow]

Hi @Leavrth. Thanks for your PR.

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[codecov]

Codecov Report

❌ Patch coverage is 55.76923% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.6861%. Comparing base (41045f1) to head (07ff254).
⚠️ Report is 687 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #60979        +/-   ##
================================================
+ Coverage   73.1476%   74.6861%   +1.5384%     
================================================
  Files          1724       1724                
  Lines        477139     477201        +62     
================================================
+ Hits         349016     356403      +7387     
+ Misses       106718      98680      -8038     
- Partials      21405      22118       +713     

Flag	Coverage Δ
integration	46.0222% <55.7692%> (?)
unit	72.3733% <55.7692%> (-0.0048%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.7804% <ø> (ø)
parser	∅ <ø> (∅)
br	62.5301% <55.7692%> (+14.9659%)	⬆️

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[Leavrth]

/retest

[tiprow]

@Leavrth: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[Leavrth]

/retest

[tiprow]

@Leavrth: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

In response to this:

/retest

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: 3pointer, BornChanger

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• br/OWNERS [3pointer,BornChanger]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-05-14 02:55:05.903583078 +0000 UTC m=+500172.051544319: ☑️ agreed by 3pointer.
• 2025-05-14 05:33:03.4547114 +0000 UTC m=+509649.602672618: ☑️ agreed by BornChanger.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #63284.
But this PR has conflicts, please resolve them!