feat: Content Steering HLS Pathway Cloning

[wseymour15]

Description

Implementation for HLS Pathway cloning for content steering. See the spec here: https://datatracker.ietf.org/doc/draft-pantos-hls-rfc8216bis/

Whenever we get a response from the content server with a PATHWAY-CLONES array, we need to add, update, or delete playlists and media based on the data we receive. A pathway clone object tells us information about a new pathway that should be created/updated based off of another pathway.

Specific Changes proposed

• Store the pathway cloning data retrieved from the server reponse in the content steering controlelr.
• Add a new pathway with playlist and media data when the pathway clone did not exist previously.
• Update playlist and media data from a previously existing pathway clone when we get new data from the pathway clone object.
• Delete playlist and media data from a pathway clone that is no longer in the content steering server response.
• Unit tests for this functionality.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

Merging #1432 (2e484f0) into main (dd5e2af) will decrease coverage by 0.66%.
Report is 6 commits behind head on main.
The diff coverage is 98.70%.

@@            Coverage Diff             @@
##             main    #1432      +/-   ##
==========================================
- Coverage   85.98%   85.33%   -0.66%     
==========================================
  Files          42       42              
  Lines       10428    12305    +1877     
  Branches     2412     2928     +516     
==========================================
+ Hits         8967    10501    +1534     
- Misses       1461     1804     +343     

Files	Coverage Δ
src/content-steering-controller.js	99.45% <100.00%> (+0.02%)	⬆️
src/manifest.js	93.57% <100.00%> (ø)
src/playlist-loader.js	96.26% <100.00%> (+1.06%)	⬆️
src/playlist-controller.js	95.78% <95.34%> (-0.03%)	⬇️

... and 2 files with indirect coverage changes

📣 Codecov offers a browser extension for seamless coverage viewing on GitHub. Try it in Chrome or Firefox today!

[adrums86]

Looks great, just a couple of questions.

[adrums86]

This looks great overall, 1 minor style question.