Fix capLevelToPlayerSize after hiding player and maintain stable selection when aspect ratio changes

[robwalch]

This PR will...

• Continue to poll player size when not displayed with capLevelToPlayerSize
  • Fixes capLevelToPlayerSize incorrect behaviour after HTML video element is not displayed #5611
• Prevent changes in aspect-ratio from causing capping to toggle back and forth

Why is this Pull Request needed?

Makes cap-level-controller continue to detect player size changes after it has been hidden and shown again.

Also prevents autoLevelCapping from bouncing back and forth when aspect ratio changes slightly between renditions because of rounded height values. To repro set player size to 426px with first BBB test stream.

Are there any points in the code the reviewer needs to double check?

The first issue (#5611) can be worked around by toggling capping after displaying the media element again:

hls.capLevelToPlayerSize = false;
hls.capLevelToPlayerSize = true;

This could be done at any time the size/layout of the media element is changed to perform a timely update of autoLevelCapping on requestAnimationFrame.

If you are already using HLS.js in a player that reads/writes page layout and controls the media element and observes its dimensions, then it is recommended to not use cap-level-controller. Instead batch the work of reading player width and height with existing checks in your player, and set hls.maxAutoLevel externally.

Resolves issues:

Fixes #5611

Checklist

• changes have been done against master branch, and PR does not conflict

[pmmf85]

Tested locally. After these changes I can confirm that width and height are detected correctly, even after video HTML element becomes hidden and then visible again.

[pmmf85]

Tested locally, both in demo as in my app, capLevelToPlayerSize behaves as intended after changes. Reported issue resolved as well.