Replace libkeybinder by a GAction under Wayland

[gsemet]

See FeatHub vote here.

Under wayland, libkeybinder requires to force use of XWayland (X11 backend). This does not seem to do the job since some complain Guake does not show up if the current focussed application if a GTK3 application.

It seems the cleaner solution would be to develop a GAction (see #1109) to replace the use of libkeybinder under Gnome/Wayland. This would not completely replace libkeybinder, since other DE (such as XFCE or KDE) won't see the "GAction". Maybe a plugin system should be developed to easily extend the global hotkey support in the future (plugins/hotkeys/{gnome.py,kde.py,xfce.py,libkeybinder.py...}).

[stanfieldr]

@chaintip 90 days

[chaintip]

Thank you @alwaysAn0n! 0.13651537 BCH| ~ 58.23 USD has now been tipped to this issue.
To claim this bounty, get a pull request merged with @chaintip fixes #1343 in the creation comment.