[Flang] Replace notifyMatchFailure with TODO hard failures

For unimplemented patterns we revert to using TODO hard failures instead of
notifyMatchFailure.

For fir.select_type revert to using mlir::emiterror.
For the fir.embox TODO on a type with len params we cannot add a test since the type cannot be converted to llvm.

Adding negative tests using not and checking for the error message.
TODO exits with an error in a build without assertion but aborts in a
build with assertions. Abort requires using not with the --crash
option. The two different usages of not is handled by using a custom
command %not_todo_cmd which is converted to not or not --crash
depending on the presence or absence of assertions. Using llvm-config
to check the presence of assertions.

Reviewed By: clementval, awarzynski

Differential Revision: https://reviews.llvm.org/D114371