USD Import - please support sensor size

usd_reader_camera.cc reads horizontal and vertical aperture, but does not store them, so camera field of view is always wrong (inconvenient/annoying to users). They need to be stored in the BKE_camera. This is labeled as TODO(@makowalski). Note sure why this isn’t pretty trivial.

Refs: developer.blender.org/diffusion/B/browse/master/source/blender/io/usd/intern/usd_reader_camera.cc developer.blender.org/diffusion/B/browse/master/source/blender/blenkernel/BKE_camera.h