const google.golang.org/protobuf/internal/genid.DescriptorProto_Extension_field_fullname

one use

	google.golang.org/protobuf/internal/genid (current package)
		descriptor_gen.go#L105: 	DescriptorProto_Extension_field_fullname      protoreflect.FullName = "google.protobuf.DescriptorProto.extension"