Refactor SteamOS session management and launcher scripts

- Removed obsolete launch_desktop.sh and launch_session.sh scripts.
- Introduced new steam-launcher script to handle Steam launching and session tracking.
- Added steam-short-session-tracker for monitoring short Steam sessions and triggering repairs.
- Created steamos and steamos-session scripts for managing the SteamOS session.
- Implemented steamos-session-select for switching between Gamescope and Plasma sessions.
- Updated SDDM configuration for autologin and session management.
- Added new systemd services and targets for managing Gamescope and Steam sessions.
- Created desktop entries and icons for ALVR and SteamOS shortcuts.
- Enhanced logging and error handling across scripts.
- Cleaned up unused systemd slice and service files.
- Updated Ansible playbook to reflect new configurations and file structures.

ansible/files/game_station/systemd/user/steam-launcher.service

@@ -0,0 +1,22 @@
+[Unit]
+Description=Steam Launcher
+After=gamescope-session.target
+PartOf=gamescope-session.target
+
+[Service]
+ExecStart=steam-launcher
+
+# Track short sessions to trigger a repair after enough failures
+ExecStartPre=steam-short-session-tracker --track-started
+ExecStopPost=steam-short-session-tracker --track-stopped
+
+# To close properly we need to kill the child of the steam wrapper, as the wrapper itself does not forward signals
+ExecStop=/bin/bash -c 'kill -TERM $(pgrep -P $MAINPID || echo $MAINPID)'
+# Disable the term signal sent from systemd, as we we handle it manually above
+# But still want systemd to kill the entire cgroup on timeout
+KillSignal=SIGCONT
+KillMode=mixed
+TimeoutStopSec=60
+
+Type=exec
+EnvironmentFile=%t/gamescope-environment