Shortcut UI should only show active shortcuts (make list dynamic)

[karendolan]

The keyboardShortcutsHelp shows shortcuts that are not active to the user either because the plugin is not loaded or the shortcut is disabled for some other reason. It is confusing to list shortcuts that don't do anything along with the active shortcuts. It would be cleaner to only list shortcuts that are active.

Here is a non-optimal (hardcoded) example of a dynamic keyboardShortCutsHelp plugin that uses the config file to determine the name of potentially active plugins and then query if they are loaded:
https://github.com/harvard-dce/opencast-contrib/blob/f/DCE-Paella-7-customizations/modules/engage-paella-player-7/src/plugins/es.upv.paella.override.keyboardShortcutsHelp.js

The plugin it overrides:
https://github.com/polimediaupv/paella-basic-plugins/blob/main/src/plugins/es.upv.paella.keyboardShortcutsHelp.js

This is a request to generalize a method to determine if the shortcut is functional or not in loaded player, so that only the active shortcuts are displayed in the help list.