[mlir][Transform] Make applyToOne return a DiagnosedSilenceableFailure

This revision revisits the implementation of applyToOne and its handling
of recoverable errors as well as propagation of null handles.
The implementation is simplified to always require passing a vector<Operation*>
in which the results are returned, resulting in less template instantiation magic.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D129185