webgpu/shader/execution: Fix bad WGSL generation (#762)
webgpu/shader/execution: Fix bad WGSL generation (#762)

Subcases of `webgpu:shader,execution,robust_access:linear_memory,*` tests were attempting to call `any()` on boolean scalars. No such overload exists.

Currently for these tests, only matrices, when indexed, produce a vector. So instead of checking fro `innerLength`, check the outer container type is a matrix.

Fixes 6 test cases.
gpuweb/cts,gpuweb/cts,gpuweb/cts