Rename `invalid-method-override` rule

We have lots of rules that complain about invalid method overrides of one sort or another, and we'll be adding more in the future. The `invalid-method-override` rule is specifically about Liskov violations, but its name doesn't reflect that currently. `unsound-method-override` might be better, though it's still not great. Maybe `incompatible-method-override`?

No files, tests, or entry points are named. First locate the implementation and references for the `invalid-method-override` rule, then review the proposed names and project conventions. Done means agreeing on a replacement that reflects Liskov violations and consistently renaming the rule.

Written by the indexing model from the issue text.