Code improvements for media pages

[YourOrdinaryCat]

Resolved / Related Issues
Closely related to #160

Details of Changes
This pull request aims to make the app follow the MVVM pattern more closely, which involves:

• Decoupling: the current way we handle collections is from MainViewModel, which has every single collection. This means we have a lot of boilerplate just to reset filtering and sorting, and it makes saving session state more difficult
• Less repetition: there's a lot of repeated code when it comes to handling playback and other actions within a given page. This makes the code behind of every page far larger than necessary, which can lead to inconsistencies when triggering different actions

Validation
Not yet finished.

Screenshots / Videos (optional)
Not necessary, at least for now.

[YourOrdinaryCat]

AlbumsPage has DataTemplate related bugs as of now - mostly hangs and memory leaks when switching, and the template not applying sometimes. Switching to a custom control there is likely necessary, will add that within the next few commits.

[itsWindows11]

Looks good to me, but there are some changes that need to be addressed before merging.

[itsWindows11]

Also, use the ContextRequested event for the context menu for the lists instead of RightTapped which only handles right click.

[YourOrdinaryCat]

Should be good now.

[itsWindows11]

LGTM