prop(unicorn): Replace logout button with system menu

[ajstrongdev]

Replace the logout button on the left hand side of the panel with a system menu similar to that found on macOS.

I have quickly mocked up an example utilising a custom menu found here: https://www.xfce-look.org/p/1529470

• Changes will be required to make it fit for Rhino Linux, and i do believe a custom icon would be better for the icon as opposed to the standard Rhino Linux icon.

[oklopfer]

I want a better icon for this but yeah this menu is fire

[ajstrongdev]

I want a better icon for this but yeah this menu is fire

Yeah, the menu was just temporary to show this off. Moving to "todo"

[ajstrongdev]

I am not happy with my current implementation of this and plan to rework it in time for 2023.5, moving to rollover.