- add MediaStyle notifications for Background and Popup playback
- reduce excessive notification updating ( / recreating of Notification.Builder object) when playing background / popup media
- add new buffering state indicator (can be disabled)
- upscale close icon / downscale replay icon
- add notification slot settings
- move notification settings to appearance
- fix Metadata (song title, artist and album art) sometimes not being set correctly
- other misc notification fixes

Co-authored-by: wb9688 <wb9688@users.noreply.github.com>

Improve builder parameters
Reorder code and extract large icon function
service.startForeground() now is also provided with service type in android versions >= Q

Have the notification recreate only when strictly necessary, and recreate it if there was a timeline change, fixing the seekbar not updating at all sometimes

- ACTION_BUFFERING was just wrong: why should the user be able to trigger the internal onBuffering() state by pressing on the buffering button? So that was replaced by a null intent, doing nothing.
- Now updating notification in onBuffering() only when buffering actions are not already buffering, to prevent useless updates