expression: fix charset conversion warning and error behavior (#51191)

[ti-chi-bot]

This is an automated cherry-pick of #51191

What problem does this PR solve?

Issue Number: close #50295

Problem Summary:

The error cannotConvertString should have three different behaviors:

1. Explicit cast, and SQL_MODE is strict: it'll return NULL and add a warning.
2. Explicit cast, and SQL_MODE is not strict: it'll return truncated string and add a warning.
3. Implicit cast: it'll return an error.

TiDB returns error in all cases, so it's not compatible.

What changed and how does it work?

Fix the behavior of from_binary function. Now it's only fixed on TiDB, and will need some modification on TiKV as well.

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

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 16 lines in your changes are missing coverage. Please review.

Please upload report for BASE (release-7.5@33cae3a). Learn more about missing BASE report.

❗ Current head 4964392 differs from pull request most recent head 48f3478

Please upload reports for the commit 48f3478 to get more accurate results.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #53470   +/-   ##
================================================
  Coverage               ?   71.9998%           
================================================
  Files                  ?       1411           
  Lines                  ?     410069           
  Branches               ?          0           
================================================
  Hits                   ?     295249           
  Misses                 ?      94967           
  Partials               ?      19853           

Flag	Coverage Δ
unit	71.9998% <50.0000%> (?)

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

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.4014% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Defined2014, zanmato1984

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [Defined2014,zanmato1984]
• pkg/expression/OWNERS [zanmato1984]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-22 07:25:51.09441657 +0000 UTC m=+2242904.851552320: ☑️ agreed by zanmato1984.
• 2024-05-22 07:26:54.589395971 +0000 UTC m=+2242968.346531545: ☑️ agreed by Defined2014.