Add more timestamp tests

[greggman]

• Test that resolving a timestamp twice produces the same result.
• Test that slots that are never used resolve to zero.

Note: the issue about BigUint64Array is typescript 5.2.2 types I think. IIRC sometime between 5.2.2 and 5.9.3 fix it. They're now on 6.0.2 which I think broke a bunch of typedarray stuff.

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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.)
• Test have be tested with compatibility mode validation enabled and behave as expected. (If not passing, explain above.)

Requirements for reviewer sign-off:

• Tests are properly located.
• Test descriptions are accurate and complete.
• Tests provide complete coverage (including validation control cases). Missing coverage MUST be covered by TODOs.
• Tests avoid over-parameterization (see case count report).

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

[kainino0x]

LGTM % merge conflict

[github-actions]

Results for build job (at c33aa17):

+webgpu:api,operation,command_buffer,queries,timestampQuery:multi_resolve:* - 2 cases, 2 subcases (~1/case)
+webgpu:api,operation,command_buffer,queries,timestampQuery:unused_slots_are_zero:* - 2 cases, 2 subcases (~1/case)
-TOTAL: 281178 cases, 2322743 subcases
+TOTAL: 281182 cases, 2322747 subcases