Separate tests for target format supporting usage and being a color format

[kainino0x]

This splits two logically separate tests that were part of the same test before. This will make it easier to fix usage of the texture info table: Previously, it would access certain members of the info table assuming they were color, but would actually get the depth component of depth and depth-stencil formats. This wasn't really a problem because those formats were already expected to fail. But cleaner to instead just scope that test to only color formats.

Part 4 of Issue: #2495

---

Requirements for PR author:

• All missing test coverage is tracked with "TODO" or .unimplemented().
• New helpers are /** documented */ and new helper files are found in helper_index.txt.
• Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located in the test tree.
• Test descriptions allow a reader to "read only the test plans and evaluate coverage completeness", and accurately reflect the test code.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Helpers and types promote readability and maintainability.

When landing this PR, be sure to make any necessary issue status updates.