Socket connect no longer synchronous and blocking

Summary:
Never really liked this code. Before this change, calls to connect were blocking.

Because of this, we had to make use of promises and a bit of really not that good-looking code.

So, this change makes connect non-blocking meaning that we make full use of our event handler.

These changes contain:
- CSR is not getting generated after each failed attempt.
- Connect is no longer blocking.
- Do not report events via the handler when explicitly disconnecting.

Reviewed By: jknoxville

Differential Revision: D46853228

fbshipit-source-id: 00e6a9c7c039a756175fe14982959e078d92bacb

iOS/FlipperKit/FlipperPlatformWebSocket.mm

@@ -181,11 +181,6 @@ static constexpr int connectionKeepaliveSeconds = 10;
 
   [_dispatchQueue cancelAllOperations];
   [_dispatchQueue waitUntilAllOperationsAreFinished];
-
-  // Manually trigger a 'close' event as SocketRocket close method will
-  // not notify the delegate. SocketRocket only triggers the close event
-  // when the connection is closed from the server.
-  _eventHandler(facebook::flipper::SocketEvent::CLOSE);
 }
 
 - (void)send:(NSString*)message