Add test to sync RN github flow configs

Summary:
Adds three more tests:

* compare RN github ios and android flowconfigs
* compare xplat/js ios flowconfig with RN github ios flowconfig
* compare xplat/js android flowconfig with RN github android flowconfig

Reviewed By: TheSavior

Differential Revision: D9191176

fbshipit-source-id: 34f3644ffc5a26d3bdfd94b6c05a138407aaedeb

.github.flowconfig.android

@@ -51,8 +51,8 @@ module.system.haste.name_reducers='^.*/\([a-zA-Z0-9$_.-]+\.js\(\.flow\)?\)$' ->
 # strip .js or .js.flow suffix
 module.system.haste.name_reducers='^\(.*\)\.js\(\.flow\)?$' -> '\1'
 # strip .android suffix
-module.system.haste.name_reducers='^\(.*\)\.ios$' -> '\1'
 module.system.haste.name_reducers='^\(.*\)\.android$' -> '\1'
+module.system.haste.name_reducers='^\(.*\)\.ios$' -> '\1'
 module.system.haste.name_reducers='^\(.*\)\.native$' -> '\1'
 module.system.haste.paths.blacklist=.*/__tests__/.*
 module.system.haste.paths.blacklist=.*/__mocks__/.*