feat: expand Calamares installer with DM chooser, explicit DE packages, and custom packages module

- Add packagechooser@dm instance for display manager selection (SDDM/LightDM/LXDM/LY)
- Expand desktop environment package lists (Xfce MATE LXQt i3) with explicit packages
- Change plasma -> plasma-meta and lsb-release -> antergos-lsb-release
- Add bootloader, displaymanager, grubcfg, postcfg, services-artix module configs
- Install antergos-release, antergos-wallpapers, antergos-grub-theme via basestrap
- Add custom packages/main.py with one-at-a-time install and --overwrite='*'
- Add --overwrite='*' to basestrap main.py for pacman -Sy operations

iso-profiles/antergos/live-overlay/etc/calamares-online/settings.conf

@@ -7,6 +7,7 @@ sequence:
         - locale
         - keyboard
         - packagechooser
+        - packagechooser@dm
         - netinstall
         - partition
         - users
@@ -37,6 +38,11 @@ sequence:
     - show:
         - finished
 
+instances:
+- id:       dm
+  module:   packagechooser
+  config:   packagechooser_dm.conf
+
 branding: antergos-next
 
 prompt-install: false