statistics: refactor common functions into subscriber

[Rustin170506]

What problem does this PR solve?

Issue Number: ref #57871

Problem Summary:

What changed and how does it work?

Split from #57872

This PR simply moved the common functions into subscriber.go because we will drop these files in upcoming PRs. I am doing this now to reduce the changes needed in the next PR.

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

[Rustin170506]

🔢 Self-check (PR reviewed by myself and ready for feedback.)

[codecov]

Codecov Report

Attention: Patch coverage is 59.61538% with 84 lines in your changes missing coverage. Please review.

Project coverage is 73.8150%. Comparing base (93295c2) to head (4c1d3d1).
Report is 101 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #58127        +/-   ##
================================================
+ Coverage   73.1325%   73.8150%   +0.6825%     
================================================
  Files          1675       1705        +30     
  Lines        461920     469992      +8072     
================================================
+ Hits         337814     346925      +9111     
+ Misses       103353     101592      -1761     
- Partials      20753      21475       +722     

Flag	Coverage Δ
integration	45.9044% <0.0000%> (?)
unit	72.2916% <59.6153%> (+0.0312%)	⬆️

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	45.9728% <ø> (+0.0360%)	⬆️

[elsa0520]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elsa0520, lance6716

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-10 07:55:24.529592194 +0000 UTC m=+338714.618394732: ☑️ agreed by elsa0520.
• 2024-12-10 10:46:04.734167533 +0000 UTC m=+348954.822970061: ☑️ agreed by lance6716.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #58459.