Added default constructor to LeapXRHandProvider with [Preserve] attri…

[MaxPalmer-UH]

…bute to fix issue using XRHands with Ultraleap data on Quest

Summary

Attempting to use XRI with XRHands and a Leap2 on a Quest can cause issues. The XR Hands subsystem bridge to pipe data from the LeapXRProvider to the XR Hands subsystem fails, the attempt to call Activate.CreateInstance for the LeapXRHandProvider type throws as a default constructor cannot be found. It appears an empty constructor is needed with the [Preserve] attribute.

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• [ ] Create or edit test cases here
• [x] Add a CHANGELOG entry for this change.
• [x] Ensure documentation requirements are met e.g., public API is commented.
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• [ ] All tests must be ran and cover all scenarios (If not, add new tests to the cycle and run them).
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