Replace Type Transform

[dave-sub360]

We currently have a grpc protobuf that uses the google timestamp protobuf google.protobuf.Timestamp. Currently this creates a new type but we would like to map fields with this type to the DateTime scalar provided by graphql-scalars. This would allow us to then use other gRPC and graphql-codegen features to use Date objects on the client. Currently you can use the replace-field transform but this would require to map out every field that uses this type. It would be valuable to have a replace-type transform that could replace all the current types with a new one without a large amount of configuration in the .meshrc.yaml file.