Tracking settings refactor

[zmerp]

I'm making this PR early for feedback. Please check the settings.rs file. CI failures are normal since I did not bother with any other file

Some notes:

• As part of this PR I will add a tracker mapping system
• Hand skeleton and buttons will be send to the proper OpenVR device, regardless of the mapping defined in the Inputs tab
• The split of sources/inputs and outputs/sinks will require adding and updating presets to make it usable