[Overlay] Use standing space

[TheButlah]

We had changes in SlimeVR/SlimeVR-OpenVR-Driver#24 that switched the tracking space from raw to "standing". We need to account for this change in the overlay.

[TheButlah]

Mentioning @kitlith in case he wants to tackle this

[kitlith]

some of the PRs made to ovr_overlay are necessary for this. (you may as well just assign me for this)

overlay has already been switched to standing, but everything else is now using a variant that ignores playspace movement, which is why changes are still necessary

[TheButlah]

some of the PRs made to ovr_overlay are necessary for this.

Working on reviewing them. Could you link the ones that block this issue?

[kitlith]

TheButlah/ovr_overlay#8 and TheButlah/ovr_overlay#9, though the first one needs to be rebased and worked on a bit now that you merged TheButlah/ovr_overlay#11

I'll get that rebased now.