Add immediate size validation tests for pipeline layout creation.

[shaoboyan091]

immediateSize attribute is used for pipeline layout creation. It requires immediateSize must be a multiple of 4 and immediateSize must be smaller or equal to maxImmediateSize.

Issue: #

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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 6324694):

+webgpu:api,validation,createPipelineLayout:immediate_data_size:* - 8 cases, 8 subcases (~1/case)
-TOTAL: 286009 cases, 2344986 subcases
+TOTAL: 286017 cases, 2344994 subcases

[Copilot]

Pull request overview

This PR adds validation tests for the experimental immediateSize attribute used in pipeline layout creation. The tests verify that immediateSize must be a multiple of 4 and must not exceed device.limits.maxImmediateSize.

Changes:

• Added a new test immediate_data_size to validate immediateSize parameter constraints
• Added supportsImmediateData helper function to check for immediate data support

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/webgpu/api/validation/createPipelineLayout.spec.ts	Added validation test for immediateSize parameter with edge case coverage including valid/invalid multiples of 4 and boundary values
src/common/util/util.ts	Added supportsImmediateData helper function to detect immediate data feature support through prototype and language feature checks

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.

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[shaoboyan091]

This test case caught a validation issue in Dawn which doesn't check alignment during pipeline layout creation.