Summary:
This deprecates the `getPlugin(String)` method and introduces
a `getPluginByClass(Class<T>)` instead which avoids having
to `instanceof`-check and then cast the result, which provides
a nicer experience for Java users.
Reviewed By: jknoxville
Differential Revision: D13277568
fbshipit-source-id: fb7b5b8c0180470ef0ad322559b5b7424520848b
214f112c14