WebGPU: Tests failing in tests/compute

[aleino-nv]

The following tests are currently failing for wgpu.
This task is about triaging these issues -- either fix on the spot or file a more detailed task.

1. tests/compute/buffer-type-splitting.slang
2. tests/compute/cbuffer-legalize.slang
3. tests/compute/compile-time-loop.slang
4. tests/compute/constexpr.slang
5. tests/compute/discard-stmt.slang
6. tests/compute/func-param-legalize.slang
7. tests/compute/func-resource-param.slang
8. tests/compute/global-init.slang
9. tests/compute/interface-shader-param-in-struct.slang
10. tests/compute/interface-shader-param.slang
11. tests/compute/kernel-context-threading.slang
12. tests/compute/loop-unroll.slang
13. tests/compute/matrix-layout.hlsl.3
14. tests/compute/non-square-column-major.slang
15. tests/compute/non-square-row-major.slang
16. tests/compute/row-major.slang

[aleino-nv]

I looked closer at the above failures and categorized them according to the following issues (some new/old, some open/closed):

1. WGSL: Missing capability for ByteAddressBuffer::Load #5221 (comment) (RWByteAddressBuffer emits array with no type field.)
   • Tests
     1. buffer-type-splitting
2. slang-RHI/WebGPU: Binding missing from bind group layout #5222 (WGPU error: Binding doesn't exist)
   • Tests
     1. cbuffer-legalize
3. WGSL: Nested structures are not allowed for entry point IO #5226 (WGPU error: nested structures cannot be used for entry point IO)
   • Tests
     1. compile-time-loop
     2. constexpr
     3. discard-stmt
4. slang-test/WGPU: unfilterable-float type sampler used to filter #5227 (WGPU error: sampler with "unfilterable-float" sample type used to filter)
   • Tests
     1. func-param-legalize
5. WGSL: Passing runtime-sized arrays (RWStructuredBuffer) by value #5228 (WGPU error: runtime-sized array not in 'storage' address space)
   • Tests
     1. func-resource-param
6. WGSL: Global variable declared without specifying address space #5229 (WGPU error: no address space declared for global variable)
   • Tests
     1. global-init
7. WGSL compilation: no conformances for interface #4938 (Slang error: No type conformances are found for interface...)
   • Tests
     1. interface-shader-param-in-struct
     2. interface-shader-param
8. slang-RHI/WebGPU: Binding missing from bind group layout #5222 (WGPU error: Number of entries (2) did not match the expected number of entries)
   • Tests
     1. kernel-context-threading
     2. matrix-layout(.hlsl)
     3. non-square-column-major
     4. non-square-row-major
     5. row-major
9. WGSL: Handle arrays of global shader parameters #4987 (WGSL error: array of runtime sized arrays)
   • Tests
     1. loop-unroll