Skip test_multithreaded_compute on MoltenVK.

[jimblandy]

Skip tests::test_multithreaded_compute in examples/hello-compute/src/tests.rs on MoltenVK for timeouts.

All commits should pass CI, but may be fine-grained enough that squashing makes sense. Up to you.

Various cleanups to expected failure code:

• Give test image snapshots distinctive names.

  Include the adapter name and driver name in the filenames generated to store the -actual.png and -difference.png files holding screenshots of test program output.

  Previously, the filename only incorporated the backend, but since we test the Vulkan backend on both Mac and Windows, one was overwriting the other in the artifacts.

• Upload GitHub workflow artifacts even when the test fails.

  When a test in .github/workflows/ci.yml's gpu-test fails, ensure that it uploads the artifacts anyway. These are screenshots and comparison images, so they're valuable in debugging the failure.

• Allow expected test failures to match the driver name.

  Add a new field FailureCase::driver, which must match AdapterInfo::driver if given.

  Use this in TestParameters::molten_vk_failure.

• Implement Default for FailureCase, and use it where appropriate.

  This makes it easier to add new fields to FailureCase in the future, without having to fix every use.

• Make TestParameters::specific_failure take a FailureCase.

  Make TestParameters::specific_failure take a FailureCase struct as its sole argument, thus requiring callers to label each parameter with its meaning. This is clearer than using four positional parameters.

• Introduce TestParameters::backend_adapter_failure.

  Introduce a new TestParameters builder method, backend_adapter_failure, for marking an expected failure on a specific adapter and backend. Use where appropriate.

• Introduce TestParameters::adapter_failure_skip.

  Introduce a new TestParameters builder method for skipping a test on a specific adapter. Use where appropriate.

• Update doc comments for some TestParameters methods.

  Replace references to specific_failures with outdated parameter lists with plain English explaining what each function actually does.

• Use TestParameters::backend_failure method where appropriate.

Checklist

• Run cargo clippy.
• Run cargo clippy --target wasm32-unknown-unknown if applicable.
• Add change to CHANGELOG.md. See simple instructions inside file.

Connections
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Description
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Testing
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[cwfitzgerald]

This is great stuff, have some nits, but good after

[jimblandy]

Requesting a new review, since some of the new commits are non-trivial. None of the older commits are affected.

[cwfitzgerald]

Very nice!