Extract pkg cmd abstractions and clean up all migrations (#1291)

* No using custom chromium.desktop any more

* Spacing

* Rely on $OMARCHY_PATH

* Add common pkg and cmd functions for use in migrations and elsewhere

* Simple pkg-adds

* Later migration does it

* Ensure running migrations on older installs have the new pkg/cmds available

* Spacing

* Use new abstractions

* Installed in later migration

* Needless comment

* Use new commands

* Fix package name from 'batt' to 'bat'

migrations/1754215533.sh

@@ -1,7 +1,7 @@
 echo "Enable auto-discovery of network printers"
 
 if [[ ! -f /etc/systemd/resolved.conf.d/10-disable-multicast.conf ]]; then
-  sudo pacman -S --noconfirm avahi nss-mdns
+  pkg-add avahi nss-mdns
 
   # Disable multicast dns in resolved. Avahi will provide this for better network printer discovery
   sudo mkdir -p /etc/systemd/resolved.conf.d
@@ -10,7 +10,7 @@ if [[ ! -f /etc/systemd/resolved.conf.d/10-disable-multicast.conf ]]; then
 fi
 
 if ! grep -q '^CreateRemotePrinters Yes' /etc/cups/cups-browsed.conf; then
-  sudo pacman -S --noconfirm cups-browsed
+  pkg-add cups-browsed
   # Enable automatically adding remote printers
   echo 'CreateRemotePrinters Yes' | sudo tee -a /etc/cups/cups-browsed.conf
   sudo systemctl enable --now cups-browsed.service