Add a CPU renderer implementation (#1750)

* Add a CPU renderer implementation

This change adds a CPU back-end to `gfx` and ensures that most of our existing CPU tests pass when using it.

Detailed notes:

* Most of the CPU renderer implementation is copy-pasted from the CUDA case, so they share a lot of similar logic

* The main addition to the CPU renderer is a semi-complete implementation of host-memory textures. The logic here handles all the main shapes (Buffer, 1D, 2D, 3D, Cube) and all the currently-supported `Format`s that are sample-able as-is (no D24S8). The implementation is not intended to be fast, and it currently only does nearest-neighbor sampling, but otherwise it tries to avoid cutting too many corners and should be ar reasonable starting point for a more complete (but not performance-oriented) implementation.

* Refactored the CPU prelude `IRWTexture` interface to inherit from `ITexture`, since in most cases a single type will end up implementing both. It might be worth it to collapse it all down to a single interface later.

* Changed the CPU prelude `ITexture`/`IRWTexture` interface so that it takes both a pointer *and* a size for output arguments. This change seems necessary to allow a shader variable declared as a `Texture2D<float>` to fetch a single `float` when the underlying texture might be using RGBA32F.

* Added to the `IComponentType` public API so that we can query a "host callable" for an entry point and not just a binary.

* Turned off the `-shaderobj` flag on two tests that weren't yet compatible with shader objects but still had the flag left in on the path (since previously the CPU path always used the non-`gfx` non-shader-object logic anyway)

* Disabled one test (`dynamic-dispatch-11`) that relied on the `ConstantBuffer<IInterface>` idiom that we know we are planning to chagne soon anyway.

* Made a few changes to the CUDA path to bring it into line with what I added for the CPU path. These were mostly bug fixes around indexing logic for sub-objects and resources.

* fixup

1 files changed, 24 insertions, 0 deletions

diff --git a/tools/gfx/renderer-shared.h b/tools/gfx/renderer-shared.h
index 9fe9768f4..2a77dcb93 100644
--- a/tools/gfx/renderer-shared.h
+++ b/tools/gfx/renderer-shared.h
@@ -149,6 +149,30 @@ protected:
     slang::TypeLayoutReflection* m_elementTypeLayout = nullptr;
     ShaderComponentID m_componentID = 0;
 
+    static slang::TypeLayoutReflection* _unwrapParameterGroups(slang::TypeLayoutReflection* typeLayout)
+    {
+        for (;;)
+        {
+            if (!typeLayout->getType())
+            {
+                if (auto elementTypeLayout = typeLayout->getElementTypeLayout())
+                    typeLayout = elementTypeLayout;
+            }
+
+            switch (typeLayout->getKind())
+            {
+            default:
+                return typeLayout;
+
+            case slang::TypeReflection::Kind::ConstantBuffer:
+            case slang::TypeReflection::Kind::ParameterBlock:
+                typeLayout = typeLayout->getElementTypeLayout();
+                continue;
+            }
+        }
+    }
+
+
 public:
     RendererBase* getDevice() { return m_renderer; }