[native] Fade video-playback-modal controls on tap

Summary:
Fade video-playback-modal controls on tap with reanimated.
Note: This diff isn't "complete" eg you can still pause/play when controls are at opacity of 0. Will address these concerns in subsequent diffs, this one is focused on the reanimated aspect.

Test Plan: Behaves as expected on iOS

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, palys-swm, Adrian

Differential Revision: https://phabricator.ashoat.com/D1147