OptiX matrix fixes

[tgrant-nv]

Description

This PR adds very basic support for named transforms to testrender and testshade. It's a linear scan through a list of transform names to find the corresponding matrix. Although this is a far-from-ideal solution for real world scenarios with many named transforms, it is sufficient to enable further testing and development.

Tests

No new tests have been added, but all previously-passing tests still pass. It would be possible to enable the matrix tests in the testsuite if not for some small differences in error reporting:

CPU:

Testing getmatrix for unknown space name:
ERROR: Unknown transformation "foobar"
  'foobar' matrix not found, as expected

GPU:

Testing getmatrix for unknown space name:
  'foobar' matrix not found, as expected

Checklist:

• I have read the contribution guidelines.
• I have previously submitted a Contributor License Agreement.
• I have updated the documentation, if applicable.
• I have ensured that the change is tested somewhere in the testsuite (adding new test cases if necessary).
• My code follows the prevailing code style of this project.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: tgrant-nv / name: Tim Grant (9c29449, f517e4b, 06608e1, 4dd83da, 106f7a2, 4e21fa2, c46adb7)

[tgrant-nv]

Hopefully this does not conflict too drastically with #1494.

[AlexMWells]

I don't think they have any conflicts, I think testshade and its CMakeList.txt are only files in common, so a merge/rebase might be necessary.

[AlexMWells]

LGTM

[tgrant-nv]

Thanks for taking a look, Alex.

[lgritz]

I just verified that those two PRs can be merged atop each other without conflict. Will merge this now.