hdx: Fixes for 1d luts in HdxColorCorrectionTask

[pkilgo-blz]

Description of Change(s)

This fixes a couple of issues in HdxColorCorrectionTask for users of 1d luts. We started to notice a TF_VERIFY() failure and a mostly-black/uninitialized viewport in usdview when we upgraded to OCIO 2.2 (VFX CY2023).

ERROR: Usdview encountered an error while rendering.
Error in '<PXR_NS>::HdxColorCorrectionTask::_CreateOpenColorIOShaderCode' at line 562 in file /.../pxr/imaging/hdx/colorCorrectionTask.cpp :
'Failed verification: ' !texInfo.texName.empty() && !texInfo.samplerName.empty() ''

• 2d106a1 fixes the TF_VERIFY() check.
• ec769ab initializes the lut values passed to the _TextureSamplerDesc. I was finding float4AdaptedLutValues was only conditionally initialized based on the active HgiFormat fmt.

I realize I've left some of the checklist undone but mostly just checking on interest.

Fixes Issue(s)

• Similar: USD 24.08 + OCIO 2.3, HdxColorCorrectionTask error in usdview with storm on linux #3274

Checklist

• I have created this PR based on the dev branch
• I have followed the coding conventions
• I have added unit tests that exercise this functionality (Reference:
  testing guidelines)
• I have verified that all unit tests pass with the proposed changes
• I have submitted a signed Contributor License Agreement (Reference:
  Contributor License Agreement instructions)

[jesschimein]

Filed as internal issue #USD-10435

❗ Please make sure that a signed CLA has been submitted!

[jesschimein]

/AzurePipelines run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).