Add support for the OpenXR Eye gaze interaction extension

[m4gr3d]

Builds upon #77989 and adds a second commit to address the remaining issues:

• Leverage feature tags on mobile xr platforms for the following reasons:
  • Check whether the extension should be enabled using the XR_EXT_eye_gaze_interaction feature. This allows to disable the extension for pico devices until the remaining issues has been resolved by the vendor
  • Check whether necessary permissions are granted on mobile platforms using the PERMISSION_XR_EXT_eye_gaze_interaction feature.
• Expands the feature tag api to allow Android plugins the ability to declare whether they support a feature or not
• Automatically prompt for the necessary permissions on app startup

For full compatibility, these changes require updates to the OpenXR loaders plugin done in GodotVR/godot_openxr_vendors#48.

[BastiaanOlij]

Tested this on Quest and works beautifully. I do think we need to introduce the extra project settings but other than that this works great!

[BastiaanOlij]

Btw @m4gr3d , feel free to merge your changes and mine into a single commit. You can add a Co-authored-by: Bastiaan Olij <mux213@gmail.com> into the commit message.

[akien-mga]

Thanks!