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

one use

	google.golang.org/protobuf/internal/genid (current package)
		descriptor_gen.go#L449: 	FileOptions_CsharpNamespace_field_fullname           protoreflect.FullName = "google.protobuf.FileOptions.csharp_namespace"