Flag unnecessary use of inline ignore directives

[anderseknert]

This likely entails quite some effort for a feature that will go unnoticed by most, so we should prioritize accordingly. But one thing that I'd really like to see Regal do is being able to flag inline ignore directives that aren't needed as the line of code they annotate doesn't violate the rule that is being ignored. This most commonly happens after refactoring, where code has been changed but comments haven't. But there's also a few cases where we've had false positives in our rules, and inline ignore directives have been used to silence those before a fix is shipped... only to be forgotten about later.

[anderseknert]

Thinking more about it, although probably as a separate issue, would be to flag unnecessary ignores in config too. But that would likely need to entail a new command to do the check, as running all ignored rules in each run adds unnecessary cost to each evaluation.