executor,infoschema: Add pad_attribute to collation info | tidb-test=pr/2354

[dveeden]

What problem does this PR solve?

Issue Number: close #54250

Problem Summary:

What changed and how does it work?

Check List

Tests

• [x] Unit test
• [x] Integration test
• [x] 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.

A `pad_attribute` column has been included in the `information_schema.collations` table and in the output of `SHOW COLLATION` to improve MySQL compatibility.