Add support for camera passthrough on Pimax headsets.

[mbucchia]

Not quite ripe for merge. Caveats:

• Requires unreleased pi_server with fix for hang inside pvr_getVSTStreamFormat().
• Upon disconnecting the USB of the headset, pvr_getVSTStreamFormat() will hang even with the fix (reported to Pimax).
• When using "Show camera on controllers", the camera needs 90 degrees rotation. This can be fixed by rotating the source image and also apply a similar rotation to the camera properties (in a future change).

Note: SteamVR requires proper room setup in order to display room view. An incorrect room setup (eg: upside-down room) will not do it.

With #54, double tap on the side of the headset will toggle room view.

Tested on Pimax Crystal Super.

[mbucchia]

Latest EVO (private beta testing) V1.0.0.83_202607092009 has the fix for the hang.

Do you think I should add a check on the EVO version to gate enabling the feature (which I don't think there's a good way to check outside of looking at some regkeys, perhaps HKEY_LOCAL_MACHINE\SOFTWARE\Pimax\PimaxContentPack\DisplayVersion), or you prefer a checkbox in the settings?

[mbucchia]

Note: updated PVR SDK submodule to bring in latest definitions, including the missing camera format.

[sboys3]

Does it only hang when pass-through is activated? Although I suppose if anyone has the play space boundaries set up to use the pass through, then it can be activated at any time.
Probably having both the version check and toggle would be a good idea. That way it should work by default. But it's still possible to turn it off if someone finds some edge cases.