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/modules/displaymanager.conf

@@ -0,0 +1,12 @@
+---
+displaymanagers:
+  - sddm
+  - lightdm
+  - lxdm
+  - ly
+  - greetd
+  - gdm
+  - mdm
+  - slim
+
+basicSetup: false