OpenXR missing Boundary/Guardian API

[BastiaanOlij]

Godot version

4.2.dev 80de898

System information

OpenXR

Issue description

The Godot 3 OpenXR plugin supported obtaining boundary/guardian information in order to obtain play space logic. While we do have a function in the XRInterface in Godot 4 that is supposed to retrieve this information (get_play_area) it is not implemented on the Godot 4 OpenXRInterface.

This logic needs to be ported.

Steps to reproduce

Call get_play_area, be amazed by it not returning data :P

Minimal reproduction project

Any XR project.