stmtctx: re-use the usedStatsInfo for different statements in a single session

[YangKeao]

What problem does this PR solve?

Issue Number: close #59019

Problem Summary:

Previously, the data in usedStatsInfo is allocated for each statements. If we can re-use it across different statements in a session, it'll benefit the performance.

What changed and how does it work?

Use (*sync.Map).Clear() to reset the map, and assign the existing map to the new stmtctx.

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

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.3665%. Comparing base (889bf45) to head (69ff8ea).
Report is 4 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #59021        +/-   ##
================================================
+ Coverage   73.0236%   73.3665%   +0.3429%     
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  Files          1684       1684                
  Lines        465663     466988      +1325     
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+ Hits         340044     342613      +2569     
+ Misses       104708     103434      -1274     
- Partials      20911      20941        +30     

Flag	Coverage Δ
integration	42.7732% <100.0000%> (?)
unit	72.2415% <100.0000%> (+0.0296%)	⬆️

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Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	45.3155% <ø> (+0.0835%)	⬆️