Vision docs need a refresh

[PeterJohnson]

We have a lot of old docs on retroreflective detection that should be cleaned out (maybe not removed, but certainly reduced), and the AprilTags sections beefed up. GRIP is not maintained, nor is RoboRealm, another tool that's mentioned, and conversely we hardly mention the two most common solutions for vision processing used in FRC today (PhotonVision and Limelight).