main/sxmo-common: Add a ghost package to fix upgrades

This old package had a pre-deinstall script to remove the necessary Sxmo daemons. We move those daemon management to the -dwm and -sway dedicated postmarketos packages.

The problem is that apk can eventually install/upgrade the -dwm or -sway package before removing sxmo-common. This cause a deactivation of the daemons.

To prevent this, we add back an empty sxmo-common to take place of the old one. This one does not contain the deinstall scripts. We will remove this in two stable release.

This also remove the deinstall scripts from -dwm and -sway cause I fear it would cause problems eventually. If an user add -dwm then remove it, it break their -sway setup.