fix: add branding packages to Default group, populate services-artix, create online grubcfg

- Add antergos-release, antergos-next-keyring, antergos-wallpapers to
  Default netinstall group (both global and online) so installed system
  keeps Antergos branding instead of appearing as plain Artix
- Populate services-artix.conf (both online + offline) with service names
  so SDDM, NetworkManager, dbus, etc. are enabled after install (fixes
  boot-to-TTY issue)
- Create grubcfg.conf for online mode with GRUB_THEME default so
  antergos-grub-theme is actually applied by grub-mkconfig

iso-profiles/antergos/live-overlay/etc/calamares-offline/modules/services-artix.conf

@@ -1,4 +1,24 @@
 ---
 command: artix-service
 
-services: []
+services:
+  - name: "acpid"
+    action: "enable"
+  - name: "bluetoothd"
+    action: "enable"
+  - name: "cronie"
+    action: "enable"
+  - name: "cupsd"
+    action: "enable"
+  - name: "dbus"
+    action: "enable"
+  - name: "dhcpcd"
+    action: "enable"
+  - name: "NetworkManager"
+    action: "enable"
+  - name: "power-profiles-daemon"
+    action: "enable"
+  - name: "sddm"
+    action: "enable"
+  - name: "syslog-ng"
+    action: "enable"