fix: _paused is updated when video playback pause

[giodevcoding]

Summary

Keep paused state in sync with playing state.

Motivation

I found that the video resumes from being paused automatically when foregrounding the app, which is an unexpected behavior. I wanted the playback state from the background, whether playing or paused, to persist from background to foreground to create a better experience for the users of my app.

Also a fix for #4321

Changes

Update _paused on RCTVideo alongside _isPlaying when the video playback (or time control status) changes.

I found that this was behavior was due to _paused on RCTVideo not being updated when the video is paused with native controls, as it is only updated by the setPause() method. The consequences of this are that setPause() is called within applyModifiers() which is called within applicationWillEnterForeground(). This call uses the current value of _paused (setPause(_paused)), which is false, and setPause() will play the video if the value given to it is false.

Updating _paused alongside _isPlaying keeps it update with the state of the player and fixes the issue.

Test plan

1. Open Video
2. Pause Video
3. Background App
4. Foreground App
5. Video should remain paused (or whatever it's background state was when backgrounded)

[KrzysztofMoch]

Good catch!