VR Refactor

[xezno]

I've merged in a big change to VR that is basically rewrites all of it under-the-hood, while keeping the existing API.

The main takeaways from this are:

• The API hasn't changed - you can still use Input.VR.LeftHand etc.
• VR is no longer accessible in "legacy" games. I've stubbed it out so that your games shouldn't break if they were using VR optionally, but VR-only games will all be non-functional now. Sorry about this, you'll need to go OOG if you want to make VR content from now on; this shouldn't be a big deal though as VR has been broken for a while, and nobody's really been making content for it.
• A lot of VR issues have been fixed, but I do expect some new bugs to crop up. Feel free to throw a new issue up or just drop them here, I don't mind - ideally we want these to be identified and fixed as quickly as possible.
• Currently there's no Vulkan support or companion view - these are planned in the very near future
• Because of a rendering bug you'll have to disable AO proxies with r_aoproxy_enable 0

If you've got any questions or concerns drop them below and I'll try to address them. Please do include some info about your setup (running vr_info in the console should output everything we need) and a repro if possible 👍

[ShadowBrian]

Not currently usable in scene editor yet, I get one eye pure white the other one works but I can't set the VR Anchor position and I can't get hand position data either, Input.VR.LeftHand.Transform is marked obsolete so I have no idea if that's what I'm supposed to use.

[xezno]

Looking into this