Move xplat/sonar/xplat/Sonar* to Flipper*

Summary:
Part of the Sonar -> Flipper rename
Intentionally left externally visible buck target as Sonar for now to minimize diff size.

Reviewed By: passy

Differential Revision: D9871684

fbshipit-source-id: 6926eb62c578a05cd895745c75ed7da3cfe965b5

xplat/Flipper/SonarStep.h

@@ -0,0 +1,32 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+
+#pragma once
+
+#include <string>
+
+class SonarState;
+
+class SonarStep {
+ public:
+  /* Mark this step as completed successfully
+   * failing to call complete() will be registered as a failure
+   * when the destructor is executed. */
+  void complete();
+
+  // Mark the step as failed, and provide a message.
+  void fail(std::string message);
+
+  SonarStep(std::string name, SonarState* state);
+  ~SonarStep();
+
+ private:
+  std::string name;
+  bool isLogged = false;
+  SonarState* state;
+};