feat (helper): add field reflection helpers getMessageType and isFieldMessage
feat (helper): add field reflection helpers getMessageType and isFieldMessage

moul/protoc-gen-gotemplate,gfanton/protoc-gen-gotemplate,moul/protoc-gen-gotemplate,gfanton/protoc-gen-gotemplate,moul/protoc-gen-gotemplate,moul/protoc-gen-gotemplate