[dbtool] Add migration to verify/fix char_flags count

[WinterSolstice8]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Fixes root cause of #5663
If char_flags row count is less than char row count, that means the previous migration (or some other anomaly) failed before this PR to fix the previous migration fix #5647

The query it runs is safe to repeatedly run.

Steps to test these changes

run dbtool.py migrate, see it work if you need it, and to skip if you don't.