Currently playlist items do not span the full width; there is a bunch of
complicated logic to determine the margins and playlist's width. This
makes the display look unbalanced and causes a subtle bug visual bug
(see BUG: below).
This patch resolves both issues by making playlist items visually stick to
both edges of the playlist, just like the category selector list items do.
This patch also does a bit of necessary code cleanup for the playlist states.
I tested this out quite a bit but to make sure there were no regressions but
both edges of the playlist, just like the category selector list items doit's possible that I missed something so more testing may be needed.
BUG: 408210