br: update global checkpoint ts for safepoint

[Leavrth]

What problem does this PR solve?

Issue Number: close #59094 ref #58031

Problem Summary:
the safepoint error is skipped if the new safepoint is less than the minimal safepoint of the cluster or if occurs an error when put the new safepoint to PD.

What changed and how does it work?

1. use global checkpoint ts to update safepoint.
2. pause the task if the new safepoint is less than the minimal safepoint of the cluster.

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

[ti-chi-bot]

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[codecov]

Codecov Report

Attention: Patch coverage is 56.52174% with 10 lines in your changes missing coverage. Please review.

Project coverage is 74.5652%. Comparing base (9c37399) to head (e976f69).
Report is 22 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #59210        +/-   ##
================================================
+ Coverage   73.0489%   74.5652%   +1.5162%     
================================================
  Files          1684       1705        +21     
  Lines        466386     480102     +13716     
================================================
+ Hits         340690     357989     +17299     
+ Misses       104751      99663      -5088     
- Partials      20945      22450      +1505     

Flag	Coverage Δ
integration	46.0131% <4.3478%> (?)
unit	72.2249% <52.1739%> (-0.0169%)	⬇️

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

Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	60.0213% <56.5217%> (+14.6981%)	⬆️