Fix scope resolution operator working with module/interface (#4890)

[ba-sc]

Closes #4890

[chykon]

There is a problem with the t_class_mod_bad test: since the check for an invalid left operand of the scope resolution operator now happens earlier, the new error message overrides the expected old message.

Should I update the expected output for this test? Or do I need to come up with some other solution?

Also need to think about what to do with the existing check code:

https://github.com/verilator/verilator/blob/a951446f9bb085549c093ed5890f78f98a886f51/src/V3LinkDot.cpp#L3631-L3640

Perhaps it should be improved further? On the other side, the new code allows you to throw an error earlier.

[wsnyder]

Maybe have the test mis-reference a variable? The intent is to give code coverage to that (older) message - so whatever's needed to make it fire. (Unless it's impossible which I don't think on quick reading.)

[wsnyder]

@chykon do you think you'll be able to get back to finishing this pull request?

[chykon]

I can't for now, but if someone wants to continue working on PR, I don't mind.