Allow accessing alternative clicks via touchscreen long press

[trigg]

Adds the following long press gestures to access alternative click actions:

• Extra actions on application menu launchers
• Window list menu
• Volume control mute
• Notifications D&D
• Tray items menu

Also splits the logic of click press & click release to allow these events to be cancelled correctly.

[trigg]

For rationale, on a touch-only device these features are completely impossible to reach in current release. Not major blockers but it would make sense to bring them across.

[ammen99]

I wonder whether you'd want to add this to the newly merged wireplumber widget as well? Otherwise LGTM.

[trigg]

For now go with it, I see there's quite a lot of contextual options in wp-mixer and will have to come back to it another time

[ammen99]

Alright, thanks!