Add shader execution tests on the feature subgroup-size-control

[Jiawei-Shao]

This patch adds the shader execution tests on the feature subgroup-size-control:

• The value of the built-in variable subgroup_size must equal the value of the @subgroup_size attribute.
• At least one value in the range of [subgroupMinSize, subgroupMaxSize] can be used as @subgroup_size
  attribute in a simple compute pipeline.

Issue: #4640

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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.

[github-actions]

Results for build job (at 4c11238):

+webgpu:shader,execution,shader_io,compute_builtins:subgroup_size_attribute:* - 6 cases, 6 subcases (~1/case)
-TOTAL: 281259 cases, 2322918 subcases
+TOTAL: 281265 cases, 2322924 subcases

[Jiawei-Shao]

@kainino0x @jrprice PTAL, thanks!

[jrprice]

LGTM