Add alternative LOSAngularOffsetHandRayPoseSource

[whebertML]

Fixes #548
Likely also fixes #580

Fixes the issue by adding an alternative hand ray pose source that can optionally be used that is much less affected by head rotations. To utilize the new hand ray pose source, within the MRTK XR Rig, select the Far Ray of each hand:

Then in the Inspector for each Far Ray, add an Aim Pose Source and select the LOSAngularOffsetHandRayPoseSource. Move the new pose source to the top of the list so it takes precedence, and set the hand:

Example video demonstrating the change. The white ray is the existing hand ray, the green ray is the new LOSAngularOffsetHandRayPoseSource:

org.MixedRealityToolkit.MRTK3Sample-20240125-101136.mp4

[AMollis]

@whebertML , please hold off on merging until someone at MS tests on HL2. Thank you

[whebertML]

@AMollis Sounds good. 👍 Curious how it behaves on HL2. Similar behavior on ML2 and Quest (2/3).

[shaynie]

@whebertML Thanks - I'll check it out today.

[shaynie]

It worked OK on HL2 after an initial problem when I didn't set the 'hand' field on the two pose sources. If you don't set the hand, you get errors if you try to run it in editor and the hand ray shoots out of the side of your hand on device. After configuring the pose sources correctly and rebuilding, everything worked on HL2.
I suggested to @whebertML that we try to find a way to disallow or warn of improper configuration.

[whebertML]

@AMollis @shaynie Would something like this at the top of the TryGetPose method work?

        Debug.Assert(Hand == Handedness.Left || Hand == Handedness.Right, $"The {GetType().Name} does not have a valid hand assigned.");

        XRNode? handNode = Hand.ToXRNode();

        if (!handNode.HasValue)
        {
            pose = Pose.identity;
            return false;
        }

Should be added to the existing PolyfillHandRayPoseSource as well, then, since it doesn't check for valid hand either currently.

[shaynie]

/azp run

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