Auto merge of #23857 - asajeffrey:webxr-sessions-track-draw-texture, r=Manishearth

WebXR sessions track draw texture

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Send the XR framebuffer texture to the XR session.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because we don't have webxr reftests

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