Produce tsc typings for "flipper" package

Summary: This diffs refactors tsc projects structure and structure of our custom typings to allow producing typescript typings for "flipper" package. In next diffs I'm going to use the produced typings to check compatibility of plugins with certain versions of Flipper, e.g. to check whether plugin is compatible with current "stable" and "insiders" version.

Reviewed By: passy

Differential Revision: D26997158

fbshipit-source-id: a0416c7139bf08ec9d175730da4c4c2a8768eeb7

desktop/test-utils/tsconfig.json

@@ -3,7 +3,5 @@
   "compilerOptions": {
     "outDir": "lib",
     "rootDir": "src"
-  },
-  "include": ["src"],
-  "exclude": ["node_modules", "**/__tests__/*"]
+  }
 }