### Godot version

4.2.dev 80de898d721f952dac0b102d48bb73d6b02ee1e8

### 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.
ERR_FAIL_UNSIGNED_INDEX(p_foveation_level, 4);
	OpenXRFBFoveationExtension *fov_ext = OpenXRFBFoveationExtension::get_singleton();
	if (fov_ext != nullptr && fov_ext->is_enabled()) {
		XrFoveationLevelFB levels[] = { XR_FOVEATION_LEVEL_NONE_FB, XR_FOVEATION_LEVEL_LOW_FB, XR_FOVEATION_LEVEL_MEDIUM_FB, XR_FOVEATION_LEVEL_HIGH_FB };
		fov_ext->set_foveation_level(levels[p_foveation_level]);
	}
}
bool OpenXRAPI::get_foveation_dynamic() const {
	OpenXRFBFoveationExtension *fov_ext = OpenXRFBFoveationExtension::get_singleton();
	if (fov_ext != nullptr && fov_ext->is_enabled()) {
		return fov_ext->get_foveation_dynamic() == XR_FOVEATION_DYNAMIC_LEVEL_ENABLED_FB;
	}
	return false;
}
void OpenXRAPI::set_foveation_dynamic(bool p_foveation_dynamic) {
	OpenXRFBFoveationExtension *fov_ext = OpenXRFBFoveationExtension::get_singleton();
	if (fov_ext != nullptr && fov_ext->is_enabled()) {
		fov_ext->set_foveation_dynamic(p_foveation_dynamic ? XR_FOVEATION_DYNAMIC_LEVEL_ENABLED_FB : XR_FOVEATION_DYNAMIC_DISABLED_FB);
	}
}
OpenXRAPI::OpenXRAPI() {
	
	singleton = this;
	if (Engine::get_singleton()->is_editor_hint()) {
		
	} else {
		
		int form_factor_setting = GLOBAL_GET("xr/openxr/form_factor");
		switch (form_factor_setting) {