* removed the launcher through Xorg since Steam Link can now run with a desktop env on both RaspiOS 10 and 11, choosing between the DRM or MMAL drivers. Tested on a RPI 3 (RaspiOS 10) and RPI 4 (RaspiOS 11).
* adjusted the dependencies to remove xorg/matchbox/zenity since they're not strictly necessary and added a few packages which might not be automatically installed on RetroPie. The list of the packages that `steamlink` tries to install on first run in is `$XDG_DATA_HOME/SteamLink/steamlinkdeps.txt`, I just picked the ones that are not already part of existing dependencies (`vlc` will install most of them).
* disabled the package on 64bit, since is not available there (see https://steamcommunity.com/app/353380/discussions/0/1649917420735113143/)
* config file symlinking should be done only as part of install
* makeUserDir $md_conf_root/$md_id is needed as the config directory won't be created until addPort otherwise
* replace manual invocations of "xinit" with XINIT: command prefix
* build a custom xinitrc that handles modesetting (via xrandr, setting
a mode matching the resolution and refresh instead of the mode id)
and launch of content.
* if we are already in an Xorg context, the xinitrc will be bypassed,
allowing content prefixed with XINIT: to work in all contexts without
any problem (and still supporting modesetting).
When steamlink is launched without a running Xorg server,
DualShock controllers erroneously act as both a gamepad and virtual
mouse, which causes major input conflicts in-game.
Launching from an Xorg session fixes this issue, but steamlink also
requires a window manager running in order to set the window focus
property (to allow joystick events to be processed).
Additional changes:
* switch to repository version of steamlink package
* update Help text to reflect new onscreen welcome message
* remove overscan override (issue fixed upstream).
The steamlink client will refuse to launch when overscan is enabled
(which is enabled by default on our RetroPie image), but an override
is supported.
Also expose streaming_args.txt as optional user configuration.
