`UnintentionallyCoveredCodeException` should report `ClassName::methodName` when methods are targeted

[DeveloperRob]

This might be intended / by design; however I can't see any previous reports where this has been confirmed as the intended behaviour

When an UnintentionallyCoveredCodeException exception is thrown in {performUnintentionallyCoveredCodeCheck}, the message is something like this:

- Foo
- Bar

However when the check is done, $tmp is an array in the format (Class, Method) - the returned array ($processed) is generated from $tmp[0] only. Could this be changed to implode("::", $tmp) so the output would be:

- Foo::functionA
- Foo::functionB
- Bar::functionZ

This request comes because I use CoversMethod / UsesMethod in PHPUnit - so having the method information would make finding what I have missed a lot easier.

If you are happy for the change to be made, I am happy to provide a PR with tests if required.