6.3 Mediaelement JavaScript verify all working as expected

Verify all the Medielement player JS interactions are working as expected and not throwing any errors.

Any errors resulting from the testing below should be broken out into their own tickets.

[x] Verify no console errors
[x] Test media object page, sections, adding sections, navigating sections, section highlighting.
[x] Verify Add to playlist and sync.
[x] Test highlighting of time rail, visual and functional.
[x] Verify track scrubber sync.
[x] Verify all player control icons are visible, in open/closed states, and work as expected.
[x] Verify Autoplay is the default behavior between sections and subsections.
Playlists page
[x] Verify time rail highlighting.
[x] Verify track scrubber sync.
[x] Sidebar playlist highlighting (active), and navigating.
[x] Related items navigation.
[x] Verify all panel content is loaded via AJAX successfully on initial load, and when navigating playlist items.
[x] Verify visual markers, appearance and functionality.
[x] Verify autoplay behavior when interacting, and not interacting with the player.
[x] Verify autoplay behavior when clicking in the time rail or on markers.

nulib / avalon