Change fidelity tests to use new default environment lighting

[cdata]

When we added Khronos models to our fidelity tests in #360 , we made a decision to use an environment map when staging most of them because our default environment lighting was pretty bad and Filament had no default IBL. As of #472 we have much improved default lighting conditions in <model-viewer>. We should change the environment lighting used in our tests to be based on the new default.

[cdata]

Here is an archive containing the equirectangular HDR environment map equivalent of the default lighting currently being used in <model-viewer>: lightroom_14b.zip

The three files included are:

• lightroom_14b.exr - original, in EXR format
• lightroom_14b.hdr - converted to HDR format
• lightroom_14b_offset.hdr - HDR offset by 90º

[elalish]

@cdata I'm guessing we'll still want to keep a few with other environment maps, just for breadth of testing, right? Anyway, this also seems like good fodder for the 0.5 rendering work.