br: fix checkpoint path (#55266)

[ti-chi-bot]

This is an automated cherry-pick of #55266

What problem does this PR solve?

Issue Number: close #55265

Problem Summary:
WalkDir the path {bucket}/{prefix}//{sub-dir} get the object {bucket}/{prefix}//{sub-dir}/object, but ReadFile the object {bucket}/{prefix}//{sub-dir}/object cannot find it.

What changed and how does it work?

/checkpoints -> checkpoints

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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.1@f29a4ea). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #55297   +/-   ##
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  Coverage               ?   72.5766%           
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  Files                  ?       1467           
  Lines                  ?     435983           
  Branches               ?          0           
================================================
  Hits                   ?     316422           
  Misses                 ?      99069           
  Partials               ?      20492           

Flag	Coverage Δ
unit	72.5766% <ø> (?)

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

Components	Coverage Δ
dumpling	52.9656% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	41.5576% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BornChanger, Leavrth

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Needs approval from an approver in each of these files:

• br/OWNERS [BornChanger,Leavrth]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-11 08:25:09.143286907 +0000 UTC m=+426899.232089449: ☑️ agreed by BornChanger.
• 2024-12-12 04:59:52.991561375 +0000 UTC m=+500983.080363917: ☑️ agreed by Leavrth.

[Leavrth]

/retest