[FEATURE] improvements for checkpatch.sh commit checks

[raiden00pl]

Is your feature request related to a problem? Please describe.

It seems that the commit check is still not working properly. Some edge cases are not checked and git log still looks bad:

I think we need to check if the new line is inserted directly after the committee title, otherwise it is easy to bypass the commit title length check

[linguini1]

It would also be good if the CI check can verify that PR's labeled with the breaking change label have a ! before the : in the commit message, and a 'BREAKING CHANGE: ...' description right before the sign-off.

This would catch message format incorrectness in #17244.