Initialise flipper-ui-browser with socket connection

Summary:
This diff sets up the socket connection between flipper-browser and flipper-server, and verifies that the initial UI initialisation work (e.g. `get-config` command works). The initial RenderHost is initialised as well based on the config and browser APIs.

Note that flipper-ui-core itself isn't started yet, as that has still a plethora of node imports, so Metro will correctly refuse to bundle

Not in this diff
* remove Node usage from flipper-ui-core
* implement all RenderHost APIs

Reviewed By: aigoncharov

Differential Revision: D32644074

fbshipit-source-id: 2c8065caf0191771a3867b69a431ca50eeb7a5a3

desktop/flipper-ui-browser/src/HMRClient.tsx

@@ -270,7 +270,7 @@ function showCompileError() {
   // Symbolicating compile errors is wasted effort
   // because the stack trace is meaningless:
   (error as any).preventSymbolication = true;
-  (window as any).flipperShowError?.(message);
+  window.flipperShowError?.(message);
   throw error;
 }