add pipewire.desktop autostart and configure SDDM Wayland compositor

Place pipewire.desktop in root-overlay /etc/skel/.config/autostart/
so PipeWire starts via XDG autostart on login via the patched
artix-pipewire-launcher (now supports dinit in our pipewire fork).

Configure SDDM [Wayland] section with kwin_wayland compositor
command for a Wayland-native greeter display.

Includes:
- buildiso: antergos theme symlinked as artix for prepare_grub
- profile.yaml: dinit-user-spawn -> userspawn-dinit, added
  dbus-dinit-user, pipewire-pulse-dinit, userspawn-dinit to livefs,
  antergos-lsb-release
- services-artix.conf: dinit-user-spawn -> userspawn
- basestrap.conf: xlibre-xserver for online install
- pacman.conf: IgnorePkg xorg-server to avoid conflict with xlibre
- sddm.conf: Wayland compositor command
- common.yaml: cleanup (dedup lsb-release, vi->ex-vi-compat,
  remove artix-grub-theme, jack2, noto-fonts-emoji)
- iso-x86_64.conf: IgnorePkg xorg-server for ISO build

iso-profiles/antergos-minimal/root-overlay/etc/skel/.config/autostart/pipewire.desktop

@@ -0,0 +1,8 @@
+[Desktop Entry]
+Version=1.0
+Name=PipeWire Media System
+Comment=Start the PipeWire Media System
+Exec=/usr/bin/artix-pipewire-launcher restart
+Terminal=false
+Type=Application
+StartupNotify=false