executor: add new format specifier(%# %@ %.) for str_to_date expression (#22790)

[ti-srebot]

cherry-pick #22790 to release-5.0-rc
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/22813

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/22813:release-5.0-rc-a3a4a6c4da7e

---

close #22530

What's Changed: add three function to parse

1. %#: skip numbers
2. %.: skip punct
3. %@: skip alpha

How it Works: If got %# in format specifier, iterate input string and skip all number. Same for the other two.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test

Side effects

• Performance regression: No perfmance regression
• Breaking backward compatibility: No compatibility issue

Release note

• add three format specifier for str_to_date expression

[ti-srebot]

/run-all-tests

[ti-srebot]

@guo-shaoge you're already a collaborator in bot's repo.

[XuHuaiyu]

not a critical bug, do not need to cherry-pick to release-5.0-rc