*: remove stmtctx.BadNullAsWarning and use errctx to handle bad null error

[lcwangchao]

What problem does this PR solve?

Issue Number: close #50119

What changed and how does it work?

This is one step to move error handling settings from stmtctx to errctx and this PR:

• remove stmtctx.BadNullAsWarning
• use errctx to handle bad null errors (with defined as group errctx.ErrGroupBadNull).

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

[lance6716]

/approve

[codecov]

Codecov Report

Merging #50120 (88efcd5) into master (17d24f4) will increase coverage by 2.9005%.
Report is 8 commits behind head on master.
The diff coverage is 98.9899%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #50120        +/-   ##
================================================
+ Coverage   79.3235%   82.2241%   +2.9005%     
================================================
  Files          2445       2447         +2     
  Lines        673463     676986      +3523     
================================================
+ Hits         534215     556646     +22431     
+ Misses       117881      99721     -18160     
+ Partials      21367      20619       -748     

Flag	Coverage Δ
integration	49.4972% <83.9285%> (?)
unit	79.6198% <97.9798%> (+0.2962%)	⬆️

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

Components	Coverage Δ
dumpling	73.6130% <ø> (ø)
parser	∅ <ø> (∅)
br	71.9137% <50.0000%> (+3.4053%)	⬆️

[lcwangchao]

/retest

[YangKeao]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-05 06:41:28.636554355 +0000 UTC m=+2411979.673781282: ☑️ agreed by YangKeao.
• 2024-01-05 09:27:25.428191856 +0000 UTC m=+3435.012445554: ☑️ agreed by tangenta.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lance6716, tangenta, XuHuaiyu, YangKeao

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Needs approval from an approver in each of these files:

• OWNERS [XuHuaiyu,YangKeao,lance6716,tangenta]
• br/pkg/lightning/OWNERS [lance6716]
• pkg/ddl/OWNERS [tangenta]
• pkg/expression/OWNERS [XuHuaiyu]
• pkg/table/OWNERS [tangenta]

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