txn: produce warnings when fallback from bulk mode

[ekexium]

What problem does this PR solve?

Issue Number: ref #50215

Problem Summary:

What changed and how does it work?

Produce warnings when we have to fallback to standard mode if tidb_dml_type=bulk.

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

[tiprow]

Hi @ekexium. Thanks for your PR.

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[cfzjywxk]

Just a little concern.

[codecov]

Codecov Report

Merging #51697 (8d8b333) into master (2d57833) will increase coverage by 1.6160%.
Report is 23 commits behind head on master.
The diff coverage is 9.6774%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #51697        +/-   ##
================================================
+ Coverage   70.7165%   72.3326%   +1.6160%     
================================================
  Files          1473       1475         +2     
  Lines        437056     443277      +6221     
================================================
+ Hits         309071     320634     +11563     
+ Misses       108613     102326      -6287     
- Partials      19372      20317       +945     

Flag	Coverage Δ
integration	25.4799% <9.6774%> (?)

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

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	50.8401% <ø> (+4.9653%)	⬆️

[you06]

rest LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, you06

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-03-12 12:04:20.980591548 +0000 UTC m=+773488.002837937: ☑️ agreed by cfzjywxk.
• 2024-03-13 09:54:31.781060899 +0000 UTC m=+852098.803307284: ☑️ agreed by you06.