[mlir] add utilites for DiagnosedSilenceableFailure

This class adds helper functions similar to `emitError` for the
DiagnosedSilenceableFailure class in both the silenceable and definite
failure cases. These helpers simplify the use of said class and make
tranfsorm op application code idiomatic.

Reviewed By: springerm

Differential Revision: https://reviews.llvm.org/D136072