## Issue
5554: Video: loading circle sometimes does not appear until 2nd click
## What's happening
videojs behavior:
(a) A `src` change makes the Play button re-appear.
(b) An `onPlay` (or `play()`) makes the button go away.
Due to the `m3u8` header async fetch (i.e. return is potentially delayed), the initial `onPlay` (which cleared the button) that happened after user clicked Play gets negated by a potentially-delayed `src` change.
# Changes
- Manually hide the play button that is induced by the change in `src`. In the fetch-delay scenario mentioned above, the player continues to be in a 'playing' state anyway.
- But don't hide the button if paused externally (e.g. browser-level)
Restore video loading circle
Also restores the CSS for vjs-overlay which I commented out previously for *some* reason (but I don't know why, and it doesn't seem to make a difference whether I comment it out or not)
Adds custom video.js hls quality selector plugin
This allows the quality selector plugin to stay active and listen for source changes on the player to prevent the need to recreate the player when switching between MP4's and M3U8's
## Issues
5349: Remove theater mode button from player in comments
5519: Theatre mode button doesn't do anything in full screen mode [Odysse/LBRY desktop app]
## Notes
5349: Wanted to hide for 'markdown' as well, but it seems useful for 'markdown' (to clear the screen from Related), so I did not include it.
Continually recreating video.js instance on render is bad.
Instead, persist a single instance, and simply update the source and poster on the existing instance.
I'm a bit wary of adding props to this component due to the 'dispose' call, but I think 'source' and 'claim' will update together, so it shouldn't be an issue?
## Issue:
5119 "Video: Mobile UI + overlay for keyboard shortcut feedback" was disabled because the feature broke the chromecast button in Android Chrome
4913: Can't slide volume slider in pop out mode
I first tried to handle this at the floating player level, but it was impossible to hack there due to how 'react-draggable' works (it already moved the window before the "move" handler is called, so we can't do much).
Fix by overriding the dragging behavior of the videojs' VolumeBar class by not propagating the event further. It is odd that videojs didn't already do this, since it's SeekBar does stop the propagation.
