Add a check for correct Array shape in quotes.reflect.ClassOfConstant

[jchyb]

Closes #21916
I tried to supply the ClassOfConstant with multiple other broken Types, but I was unable to break it beyond the linked issue, so I ended up adding the check for only that one case. This makes sense - the backend (and thus erasure) needs to know if the Array type parameter is a primitive type, but in other cases the erasure phase needs to know only the class, without the type parameters.

It's impossible to call classOf through the quoted code ('{classOf[t]} with a boundless t will error out), so we don't need that additional check there.

There does appear to be an issue with being able to set '{List[Array]} resulting in a crash, but that is beyond the scope of this fix - I will prepare a separate issue for that (edit: reported here).