Summary:
The `UIManager` already has a lot of responsibilities and is deeply
tied with React Native's view architecture. This diff separates out a
`DeviceInfo` native module to provide information about screen dimensions and
font scale, etc.
Reviewed By: fkgozali
Differential Revision: D4713834
fbshipit-source-id: f2ee93acf876a4221c29a8c731f5abeffbb97974
Ashwin Bharambe