Add wgpu::TextureComponentType::DepthComparison

And deprecate using ::Float in the bind group layout for
"shadow textures" in the pipeline (along with a deprecation test).

Adds the ability to be used with DepthComparison only to depth textures,
this could potentially a breaking change if users where doing
depth-comparison on float32 textures but that's not supported in WebGPU.

Bug: dawn:527
Change-Id: Ib28b0443e3002e0aa2811713b9e843c2417e13e7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/30240
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>

src/dawn_native/opengl/CommandBufferGL.cpp

@@ -949,6 +949,9 @@ namespace dawn_native { namespace opengl {
                             gl.ClearBufferiv(GL_COLOR, i, appliedClearColor.data());
                             break;
                         }
+
+                        case wgpu::TextureComponentType::DepthComparison:
+                            UNREACHABLE();
                     }
                 }