dawn_native: Fallback sorting bindings in BindGroupLayout to use the binding number

This helps us merge contiguous descriptor ranges in https://dawn-review.googlesource.com/c/dawn/+/60764

Change-Id: I772262b117087ec1f1d744596be2585a5996325f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/60765
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Michael Tang <tangm@microsoft.com>

src/dawn_native/BindGroupLayout.cpp

@@ -336,7 +336,7 @@ namespace dawn_native {
                 case BindingInfoType::ExternalTexture:
                     break;
             }
-            return false;
+            return a.binding < b.binding;
         }
 
         // This is a utility function to help ASSERT that the BGL-binding comparator places buffers