Improve error for unrecognized instructions

[randall-fulton]

@stylewarning Sorry for the delay. Had a nice little Covid battle there in the middle.

The condition is exported now. I've attempted to find any other obvious usages of the new condition, but am admittedly pretty unfamiliar with quilc, so it's more than possible I'm missing something. If you had anything specific in mind, let me know and I can make the change to introduce this condition.

[notmgsk]

Thanks, @randall-fulton :D

[randall-fulton]

Thank you both for the feedback.