macosx: Add split view for genre/artist collection views audio library

While the grid of album arts is great for the album section of the audio library, it makes less sense to scroll through a list of squares meant to represent artists or genres.

In these cases it makes more sense to have the artists or genres be shown in a sidebar as a list, with the albums being the collection view items. This PR implements this, moving the audio library view closer to other music players as well as our own mockups

Screen_Recording_2022-12-24_at_19.00.18

Screen_Recording_2022-12-24_at_19.01.35

Signed-off-by: Claudio Cambra developer@claudiocambra.com