buffer_view CTS

[alan-baker]

buffer_view validation and execution CTS tests.

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 dd3cfe0):

+webgpu:api,validation,dispatch:shader_required_buffer_size:* - 19 cases, 76 subcases (~4/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:array_length:* - 78 cases, 832 subcases (~11/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:array_length,functions:* - 78 cases, 1170 subcases (~15/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:read_layout:* - 35 cases, 604 subcases (~17/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:write_layout:* - 35 cases, 604 subcases (~17/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:read:* - 4 cases, 744 subcases (~186/case)
+webgpu:shader,execution,expression,call,builtin,bufferArrayView:write:* - 4 cases, 1224 subcases (~306/case)
+webgpu:shader,execution,expression,call,builtin,bufferLength:sized_buffer:* - 5 cases, 120 subcases (~24/case)
+webgpu:shader,execution,expression,call,builtin,bufferLength:unsized_buffer:* - 5 cases, 80 subcases (~16/case)
+webgpu:shader,execution,expression,call,builtin,bufferLength:max_size_buffer:* - 6 cases, 6 subcases (~1/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:array_length:* - 78 cases, 832 subcases (~11/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:array_length,functions:* - 78 cases, 1542 subcases (~20/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:read_layout:* - 35 cases, 604 subcases (~17/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:write_layout:* - 35 cases, 604 subcases (~17/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:read:* - 4 cases, 856 subcases (~214/case)
+webgpu:shader,execution,expression,call,builtin,bufferView:write:* - 4 cases, 1224 subcases (~306/case)
-webgpu:shader,validation,decl,let:type:* - 21 cases, 21 subcases (~1/case)
-webgpu:shader,validation,decl,let:initializer:* - 10 cases, 10 subcases (~1/case)
 [snip - full report in action logs]
-TOTAL: 281361 cases, 2323132 subcases
+TOTAL: 282684 cases, 2338877 subcases