Autodesk: usdImagingGL: support for Hgi specific variants of tests

[erikaharrison-adsk]

Description of Change(s)

Support Hgi specific variants of tests to work around missing Hgi features without needing to entirely disable tests. More specifically in this PR, use separate Metal baselines for tests that have wide line primitives, since Metal only supports one pixel wide lines.

Mechanism:

register_test_with_hgi_variants(testUsdImagingGLExample
    COMMAND "... -write testUsdImagingGLExample@[email protected]"
    IMAGE_DIFF_COMPARE
        testUsdImagingGLExample@hgi_suffix@_1.1.png
    ...
    HGI_VARIANT
        Metal
        WebGPU # For the example, but might be relevant soon
)

The placeholder string @hgi_suffix@ is replaced by an Hgi suffix when necessary.

For all listed Hgi variants supported, register a suffixed test with a suffixed baseline.

• testUsdImagingGLExample_Metal => testUsdImagingGLExample_Metal_1.1.png
• testUsdImagingGLExample_WebGPU => testUsdImagingGLExample_WebGPU_1.1.png

Other supported Hgis are also register with a suffix, but use a non-suffixed baseline:

• testUsdImagingGLExample_GL => testUsdImagingGLExample_1.1.png
• testUsdImagingGLExample_Vulkan => testUsdImagingGLExample_1.1.png

Unsupported Hgis are ignored:

• testUsdImagingGLExample_GL would not be registered on Apple platforms

If none of the Hgi variants are supported, then register a single test like normal:

• testUsdImagingGLExample => testUsdImagingGLExample_1.1.png

The proper Hgi enable settings are appended to the ENV argument for all suffixed tests:

• _Metal: HGI_ENABLE_VULKAN=0;HGI_ENABLE_WEBGPU=0
• _GL: HGI_ENABLE_VULKAN=0;HGI_ENABLE_WEBGPU=0
• _Vulkan: HGI_ENABLE_VULKAN=1
• _WebGPU: HGI_ENABLE_WEBGPU=1

Link to proposal (if applicable)

• N/A

Fixes Issue(s)

• N/A

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)

[DDoS]

HgiWebGPU support was stripped for this PR, but can be re-added later when the WebGPU branch gets merged.

[jesschimein]

Filed as internal issue #USD-10555

(This is an automated message. See here for more information.)

[jesschimein]

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