Revert "[Xfce] migrate to lightdm"

This reverts commit 0a296160be4b79cb0914cffa884e4fad0b8bb8ab.
Revert "[HardenedServer] migrate to LightDM"

This reverts commit 2b914b343817cc3fc00f289852cefc125c425b01.
Revert "[Awesome] migrate to lightdm"

This reverts commit 96f0b467c031f42749e1ce11265ab3b7df138dd1.
Revert "[CoreCDX] migrate to lightdm"

This reverts commit de0bbccf2a8f656370fd24d9d9661c068ddeef56.
Revert "[E17] migrate to lightdm"

This reverts commit b8fa3f43c9a1667878fc2b0413eadb836d9ecf73.