State of 2D (aka panel) mode on Quest 3

[Tyrian]

Ok, here's my report on the current state of 2D (aka panel) mode for Steam Link on my Meta Quest 3 headset.

It works, but there's some issues. I've ordered them by criticality. Ideally, I'd like Slouken to at least say "heard" or something, about these, so that I know they're being tracked internally within Valve instead of being ignored

1) Quitting out of Steam Link (using the nice big X in the corner of the window, like we've done since 1995) in the middle of a stream is *disastrous*. Not only will this cause a black screen when you re-open Steam Link, it will keep that black screen happening until you force-quit Steam Link. However, the only way to force-quit an app on the Meta Quest 3 (right now) is to uninstall and reinstall it, or change which beta version you're on... or reboot the headset, which turns out to be the fastest option. If you safely close the stream from within the app, by using the big picture power menu, or holding "back" and selecting "Stop Streaming", it works fine. You can tell that you've got it in The Bad Mode if you open Steam Link, you get a brief logo, with no sound, then a black screen forever. Then, when you close the app again, you are treated to the startup sound, after the app closes. This is by far the most annoying bug, because it requires a headset reboot to clear. It also happens if the stream gets interrupted by, say, taking the headset off your head long enough for it to go to proper sleep.

2) You gotta connect your bluetooth controller *before* you open Steam Link. If you open Steam Link and then connect the controller, the A and B buttons will work, but nothing else. This is obnoxious, but easily fixable by turning everything off and doing things in the proper order. Wired controllers always work fine 100% of the time.

3) H264 does not work. This sucks, because it means games that don't play nice with GPU encoding (Redout 2 for example) are fairly unplayable. This is probably a headset limitation, but it'd be nice to have that confirmed, or ideally fixed.

4) The headset supports 120 FPS, and Steam Link in 3D (full VR) mode also supports 120 FPS beautifully. However, in panel mode, it's locked to 90 FPS max, and that's when you're in an "immersive" virtual environment. When you are in passthrough (the most useful mode), Steam Link is capped to 60 FPS for display, which is absurd. This might also be a headset limitation, but it bothers me because the whole point of a 120Hz display is that I can use it to display things at 120Hz.

These all show up on the current mainline branch (1245) as well as the current beta (1399)