[native] VideoPlaybackModal support for encrypted video

Summary:
Very similar to D7225 but for video. For encrypted components, the videoUri is replaced after decryption and then the actual <Video> component is displayed. Caching layer will be added later

According to react-native-video documentation:

Rendering the player component with a null source will init the player, and start playing once a source value is provided.

However, providing null source throws a warn.

Depends on D7224
Depends on D7168

Test Plan: Provided a fake encrypted mediaInfo prop, opened the modal and ensured that a spinner is displayed while decryption is in progress and controls are hidded. After successful decryption, the video starts playing.

Reviewers: atul, marcin

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D7226