Fixup pointer tests after buffer_view landed

[alan-baker]

• Pointers to runtime arrays can be declared in workgroup and uniform storage classes with the buffer_view language feature

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 418bee4):

-webgpu:shader,validation,types,pointer:type:* - 29 cases, 29 subcases (~1/case)
+webgpu:shader,validation,types,pointer:type:* - 31 cases, 31 subcases (~1/case)
-webgpu:shader,validation,types,pointer:ptr_not_instantiable:* - 15 cases, 15 subcases (~1/case)
+webgpu:shader,validation,types,pointer:ptr_not_instantiable:* - 13 cases, 13 subcases (~1/case)