[REQUEST] Reintroduce/Revamp OpenVR support

[regzo2]

As title says, OpenVR support was notably removed in https://github.com/benaclejames/VRCFaceTracking/commit/19d05c5415e455f5ffae767d6002bbb231b1d1c5 due to the Windows appx format sandboxing causing issues with SteamVR detection for some users. It's a good time to look at reintroducing it and fully integrating OpenVR hook support to launch and close VRCFT via API.