vive: Add support for the Vive Tracker Gen 1 and Gen 2.

This set of patches enables support for the Vive Trackers using a separate watchman USB dongle. Pairing the trackers to a headset was not tested, but should work the same way as it does with controllers.

As the trackers apparently do not expose any buttons, only the IMU and lighthouse data can be utilized. The IMU data is correctly printed when VIVE_CONTROLLER_SPEW=TRUE is set and can used the same way as the other controllers. Although this MR does not contain any input profiles for the device, so they are not exposed to the API.

This branch is based on !405 (merged), so it should be merged after.