Add support for Android XR

[dsnopek]

This adds the ability to export for Android XR headsets like the Samsung Galaxy XR!

• It depends on Update to Godot v4.5.1 #141 because Android XR only works with Godot 4.5.1 or newer
• It includes an update to godot_openxr_vendors 4.3.0, because Android XR support requires 4.2.0 or newer

The Samsung Galaxy XR doesn't come with controllers by default (you need to pay extra), so this really should be paired with #153, which adds hand-tracking support

Also, it has the same performance issues as the Meta Quest (and then some), so it also benefits from:

• Hide all exhibits except the current one to improve performance #143
• Limit the number of items per exhibit on web and mobile platforms #144

Marking as DRAFT because it depends on #141

[dsnopek]

Taking out of draft now that #141 is merged :-)

[dsnopek]

I've rebased this so that it depends on #153, because there are some hand-tracking related settings that I want to be able to set for Android XR. And since most folks with a Samsung Galaxy XR won't have controllers, it makes sense to me to make those changes right away, rather than doing them in a follow-up or something

[devloglogan]

Tested this out on Galaxy XR and it worked without issue! 😄 Changes look good to me. One random thing I noticed that might make sense to add is the android directory to .gitignore.

[dsnopek]

Thanks for reviewing!

One random thing I noticed that might make sense to add is the android directory to .gitignore.

Ah, that makes sense, as it's part of Godot's default .gitignore. It's not totally related to the PR, but I've gone ahead and added it anyway :-)

[m4ym4y]

looks like there's a merge conflict from another PR that was merged, I'll merge this once that's fixed

[dsnopek]

Rebased!

[dsnopek]

Rebased again :-)