expression: fix wrong flen infer for bit constant (#23867)

[ti-srebot]

cherry-pick #23867 to release-4.0
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/24266

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

git push git@github.com:ti-srebot/tidb.git pr/24266:release-4.0-2c67a8011c7c

---

Signed-off-by: lzmhhh123 lzmhhh123@gmail.com

What problem does this PR solve?

Issue Number: close #23479

What is changed and how it works?

How it Works:

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Integration test

Release note

• fix wrong flen infer for bit constant

[ti-srebot]

/run-all-tests

[ti-srebot]

@lzmhhh123 you're already a collaborator in bot's repo.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• ichn-hu
• xhebox

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[xhebox]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 5a5eddc

[ti-chi-bot]

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