Mixedrealitytoolkit-unity: Input logger scene for new devices

[Alexees]

Describe the problem

Now that there's active work on the workflow for adding additional devices to the MRTK it's rather tedious to get all the input reading from new controllers.

Describe the solution you'd like

One Testscene with a big panel one can view all the possible inputs on the device and write them down to create a new DeviceManager.
Not all input comes from the Unity.Input class, so it should probably be generic enough that you maybe just plug a different script on it and reading comes from whatever new API there is.

Describe alternatives you've considered

logging everything to the console and read that

[wiwei]

Tagging with Help Wanted - definitely would be an awesome thing to have for making new device onramp easier.

[keveleigh]

I have basically this scene lying around from the early vNext days. I'll go find it and clean it up!

[julenka]

@Davidkline-ms please don't close this issue until the scene in your PR #5902 has a scene description panel and a doc file.