Add shader validation tests on subgroup-size-control - Part II

[Jiawei-Shao]

This patch adds the second part of the shader validation tests on the extension subgroup-size-control:

• The value of @subgroup_size must be a constant expression or an override expression that resolves to an i32 or an u32.
• The value of @subgroup_size must be a power of 2.
• The x-dimension of the entry point's workgroup_size must be a multiple of the @subgroup_size value, or a pipeline creation error occurs

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 0018d19):

+webgpu:shader,validation,extension,subgroup_size_control:subgroup_size_value_must_be_const_or_override_i32_u32:* - 18 cases, 18 subcases (~1/case)
+webgpu:shader,validation,extension,subgroup_size_control:subgroup_size_constant_value_must_be_power_of_2:* - 18 cases, 18 subcases (~1/case)
+webgpu:shader,validation,extension,subgroup_size_control:subgroup_size_override_must_be_power_of_2_at_pipeline_creation:* - 7 cases, 7 subcases (~1/case)
+webgpu:shader,validation,extension,subgroup_size_control:subgroup_size_override_valid_values_no_error:* - 1 cases, 1 subcases (~1/case)
+webgpu:shader,validation,extension,subgroup_size_control:workgroup_size_x_must_be_multiple_of_subgroup_size_at_pipeline_creation:* - 36 cases, 36 subcases (~1/case)
-TOTAL: 281256 cases, 2322907 subcases
+TOTAL: 281336 cases, 2322987 subcases