arfx creation | Move SkylightFlipperClient to creation core

Summary: Want to use this from Cosmo, so pull it out to creation core so that we can share. In the process, making it not depend on Skylight specific stuff.

Differential Revision: D53758125

fbshipit-source-id: ae1d8619e38ec5ee495b67a85c3a4858356bbe84

xplat/FlipperWebSocket/FlipperWebSocket.h

@@ -36,7 +36,7 @@ class FlipperWebSocket : public FlipperSocket {
       Scheduler* scheduler,
       ConnectionContextStore* connectionContextStore);
 
-  virtual ~FlipperWebSocket();
+  virtual ~FlipperWebSocket() override;
 
   virtual void setEventHandler(SocketEventHandler eventHandler) override;
   virtual void setMessageHandler(SocketMessageHandler messageHandler) override;