Define global logger instance to be used for all logging

Summary:
The advantage of this is that anyone can now log without needing to carry around a Logger object.
Primary reason is for making metrics less intrusive in the codebase.

Reviewed By: passy

Differential Revision: D13671368

fbshipit-source-id: 162ab1351a124683aef13983fc3bcec01385cd1a

src/__tests__/server.electron.js

@@ -6,7 +6,7 @@
  */
 
 import Server, {SECURE_PORT, INSECURE_PORT} from '../server.js';
-import LogManager from '../fb-stubs/Logger';
+import {init as initLogger} from '../fb-stubs/Logger';
 import reducers from '../reducers/index.js';
 import configureStore from 'redux-mock-store';
 import path from 'path';
@@ -23,7 +23,8 @@ beforeAll(() => {
     fs.mkdirSync(flipperDir);
   }
 
-  server = new Server(new LogManager(), mockStore);
+  const logger = initLogger();
+  server = new Server(logger, mockStore);
   return server.init();
 });