br: remove timeout context to scan regions when import sst files (#53739)

[ti-chi-bot]

This is an automated cherry-pick of #53739

What problem does this PR solve?

Issue Number: close #53724

Problem Summary:
only 10 seconds to retry scan regions

What changed and how does it work?

remove timeout context to scan regions when import sst files

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

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Please upload report for BASE (release-7.1@409465c). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.1     #53854   +/-   ##
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  Coverage               ?   75.9080%           
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  Files                  ?       1212           
  Lines                  ?     403562           
  Branches               ?          0           
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  Hits                   ?     306336           
  Misses                 ?      79715           
  Partials               ?      17511           

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-11-08 09:45:52.430371524 +0000 UTC m=+3914.621240522: ☑️ agreed by BornChanger.
• 2024-11-11 03:12:09.414387503 +0000 UTC m=+239491.605256498: ☑️ agreed by 3pointer.

[3pointer]

/test unit-test

[tiprow]

@3pointer: No presubmit jobs available for pingcap/tidb@release-7.1

In response to this:

/test unit-test

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