Update webgpu/types to 0.1.50

This makes toneMapping optional which required updating a few tests to use the nullish coalescing operator when accessing it.

New vertex formats are added that require updating capability_info.ts (and tests for unorm8x4-bgra is added at the same time).

Finally dictionary types for copies are renamed throughout the CTS even if deprecated aliases are available.

Requirements for PR author:

[X] All missing test coverage is tracked with "TODO" or .unimplemented().
[X] New helpers are /** documented */ and new helper files are found in helper_index.txt.
[X] Test behaves as expected in a WebGPU implementation. (If not passing, explain above.)
[X] Test have be tested with compatibility mode validation enabled and behave as expected. (If not passing, explain above.)

Requirements for reviewer sign-off:

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

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

gpuweb / cts