Introduce an internal FDS Flipper plugin

Summary: Adding a Flipper plugin that is isolated to design systems engineering / FDS. This is essentially our dumping grounds of useful utilities for FDS. The first thing I've added is the ability to dump / view the ui tracker hierarchy, which will be useful for development / debugging.

Differential Revision: D31076277

fbshipit-source-id: 5aff639368945796dc3ebab603dadb8d43d7b699

desktop/static/icons.json

@@ -600,5 +600,8 @@
   ],
   "camcorder-live": [
     16
+  ],
+  "app-facebook-circle": [
+    16
   ]
 }