fix frankenphp_ready_workers

Author: IndraGunawan

testdata/worker-restart.php

@@ -10,4 +10,4 @@
     $ret = \frankenphp_handle_request($fn);
 } while ($ret && (-1 === $loopMax || ++$loops < $loopMax));
 
-exit(0);
+exit(0);

threadworker.go

@@ -78,6 +78,10 @@ func setupWorkerScript(handler *workerThread, worker *worker) {
 	handler.backoff.wait()
 	metrics.StartWorker(worker.name)
 
+	if handler.state.is(stateReady) {
+		metrics.ReadyWorker(handler.worker.name)
+	}
+
 	// Create a dummy request to set up the worker
 	fc, err := newDummyContext(
 		filepath.Base(worker.fileName),