Split flipper-plugin package

Summary:
flipper-server-companion depends on flipper-plugin. flipper-plugin includes dependencies that run only in a browser. Splitting flipper-plugin into core and browser packages helps to avoid including browser-only dependencies into flipper-server bundle.
As a result, bundle size could be cut in half. Subsequently, RSS usage drops as there is twice as less code to process for V8.

Note: it currently breaks external flipper-data-source package. It will be restored in subsequent diffs

Reviewed By: lblasa

Differential Revision: D38658285

fbshipit-source-id: 751b11fa9f3a2d938ce166687b8310ba8b059dee

desktop/flipper-frontend-core/tsconfig.json

@@ -11,7 +11,7 @@
       "path": "../flipper-common"
     },
     {
-      "path": "../flipper-plugin"
+      "path": "../flipper-plugin-core"
     },
     {
       "path": "../test-utils"