Improve error message when tring to export to LLVM IR with a dialect missing the interface

Dialects can be translated to LLVM IR when they have the
LLVMTranslationDialectInterface interface registered. In case the
interface isn't explicitly registered, even the LLVM dialect can't be
exported to LLVM IR. This make the error message more explicit on this.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D96729