Change "Keyboard Privacy" behavior

[Dor]

Right now, the "keyboard privacy" feature introduced with SteamVR 2.7 will suspend all tracking information from being sent to any application when the keyboard is open, this is highly disruptive in many scenarios as it results applications to treat devices as if they disconnected or as if their location is 0,0,0.

Instead, to minimize disruption I would argue that only "input" devices (controllers, or trackers used as controllers, such as when they're used to power gloves) should be affected, further more it would be better to only affect these devices when they're pointing at the keyboard, rather than when the keyboard is open, and to re-send the last location of the device before it pointed at the keyboard until it is off the keyboard again.

These changes would still achieve the intended goal, since no tracking information pointed at the keyboard could be intercepted to figure out what keys are being pressed, and would significantly improve user experience so that less people would seek to turn this privacy feature off in the new 2.8 updates.