*: avoid thundering herd problem when timeout the stats sync load (#50956)

[ti-chi-bot]

This is an automated cherry-pick of #50956

What problem does this PR solve?

Issue Number: close #50957

Problem Summary:

What changed and how does it work?

we need to load the stats cache in the background. but if we meet the timeout, we must wait constantly to retry. it will happen thundering herd. so we need to add the rand sleep to prevent it.

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

❗ No coverage uploaded for pull request base (release-7.5@1e825d3). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #51067   +/-   ##
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  Coverage               ?   71.9798%           
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  Files                  ?       1403           
  Lines                  ?     407054           
  Branches               ?          0           
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  Hits                   ?     292997           
  Misses                 ?      94341           
  Partials               ?      19716           

Flag	Coverage Δ
unit	71.9798% <0.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.2534% <0.0000%> (?)

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-08 03:44:43.307542281 +0000 UTC m=+414808.874312166: ☑️ agreed by hawkingrei.
• 2024-02-08 03:49:45.878487035 +0000 UTC m=+415111.445256910: ☑️ agreed by hi-rustin.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, hawkingrei, hi-rustin

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[hawkingrei]

/retest