Simplify reset code

[ButterscotchV]

Our current reset code is a mess, we can absolutely annihilate gyroFix and leave it to yawFix to handle the yaw offset. I also want to remove tposeDownFix, but haven't done so yet.

There's also some really confusing logic between computed trackers, the head tracker, and different reset poses. I tackled a lot of that already, but I think there's more that can be cleaned up.

TODO

• Write unit tests for computed trackers
• Write unit tests for different reset poses
• Make tposeDownFix handled locally (integrate into attachmentFix?)
• Check if manual mounting orientation affects computed trackers