statistics: remove unused LastAnalyzePos field

[Rustin170506]

What problem does this PR solve?

Issue Number: ref #55043

Problem Summary:

What changed and how does it work?

This field will never be read. So we can safely remove 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

[Rustin170506]

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

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 73.9583%. Comparing base (6463db6) to head (2e31170).
Report is 7 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #58859        +/-   ##
================================================
+ Coverage   73.1194%   73.9583%   +0.8389%     
================================================
  Files          1677       1708        +31     
  Lines        463911     472750      +8839     
================================================
+ Hits         339209     349638     +10429     
+ Misses       103860     101632      -2228     
- Partials      20842      21480       +638     

Flag	Coverage Δ
integration	45.9017% <42.8571%> (?)
unit	72.5411% <92.8571%> (+0.2455%)	⬆️

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	45.7659% <ø> (+0.0149%)	⬆️

[Rustin170506]

/retest

[Rustin170506]

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

[Rustin170506]

/test all

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: time-and-fate, winoros

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• pkg/statistics/OWNERS [time-and-fate,winoros]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-01-10 12:35:19.505413902 +0000 UTC m=+529862.794245606: ☑️ agreed by winoros.
• 2025-01-13 05:50:11.209540182 +0000 UTC m=+764754.498371886: ☑️ agreed by time-and-fate.