tools: support more qps for api bench

[CabinfeverB]

What problem does this PR solve?

If we want to support 1000K qps, we should modify the expr

Issue Number: Close #7703

What is changed and how does it work?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has the configuration change
• Has HTTP API interfaces changed (Don't forget to add the declarative for the new API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tiup:
• Need to cherry-pick to the release branch

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024
• rleungx

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[codecov]

Codecov Report

Merging #7890 (584ee60) into master (bbd3bdb) will increase coverage by 0.00%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7890   +/-   ##
=======================================
  Coverage   73.45%   73.45%           
=======================================
  Files         434      434           
  Lines       48067    48067           
=======================================
+ Hits        35306    35310    +4     
+ Misses       9718     9708   -10     
- Partials     3043     3049    +6     

Flag	Coverage Δ
unittests	73.45% <ø> (+<0.01%)	⬆️

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[CabinfeverB]

/merge

[ti-chi-bot]

@CabinfeverB: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 203ffbb

[ti-chi-bot]

@CabinfeverB: Your PR was out of date, I have automatically updated it for you.

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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