Cleanup logger

Summary: Some cleanup around Logger, like renaming `getInstance` -> `getLogger`

Reviewed By: aigoncharov

Differential Revision: D31480828

fbshipit-source-id: d2fa9dc2b45bc34d846d45e396a74b80906d3ad5

desktop/flipper-common/src/index.tsx

@@ -12,7 +12,11 @@ export {
   LoggerTrackType,
   LoggerTypes,
   LoggerArgs,
-} from './fb-interfaces/Logger';
+  getLogger,
+  setLoggerInstance,
+  NoopLogger,
+} from './utils/Logger';
 export * from './server-types';
 export {sleep} from './utils/sleep';
 export {timeout} from './utils/timeout';
+export {isTest} from './utils/isTest';