Add explicit type for _memoizedRenderer and change React and View import in FlatList (#48798)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48798

Changelog:
[General][Changed] - Added explicit type for _memoizedRenderer and changed React and View import in FlatList

Reviewed By: cortinico

Differential Revision: D68417026

fbshipit-source-id: 0af75381f6f8c33be10add940f0791b059de3473