Automatic merge from submit-queue
Generate a better Stringer method for proto types
This replaces the bad string output generated by golang/proto with gogo/protobuf stringer generation. Makes the output similar to %#v and more debuggable. We have to have a String() method to implement proto.Message, so this is strictly better.
@wojtek-t, @thockin for after your PR merges
Fixes#28756