fw/apps/system: Add music settings for volume controls and progress bar

[asyba]

Add "Show Volume Controls" and "Show Progress Bar" options with the mobile app watch settings.

When "Show Volume Controls" is hidden:
UP/DOWN buttons perform next/previous track.
The SELECT button long-press is disabled to prevent entering volume mode.

When "Show Progress Bar" is hidden:
The progress bar and time labels are hidden.
The app unsubscribes from the tick timer to save power.

core app PR: coredevices/mobileapp#148

refactor of previous work: #525

[gmarull]

feels like it would be nice to introduce at some point per-app settings, that can be controller in a menu (pretty much like in iOS), but for now lgtm

[asyba]

feels like it would be nice to introduce at some point per-app settings, that can be controller in a menu (pretty much like in iOS), but for now lgtm

I've even considered going further, though I'm not sure if it's possible. But I'd like to be able to offer, in that per-app settings, an interface where the app can be edited in many ways, such as colors, icons, positions, actions, etc.

[ericmigi]

Cool, just to confirm, this is default off and the setting only shows up on the phone side, right?

[asyba]

@ericmigi yes for default its always showing and can only be change from mobile app.
static bool s_music_show_volume_controls = true;
static bool s_music_show_progress_bar = true;