Handle empty bind group layouts

[kvark]

Example code:

        let bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor { bindings: &[] });
        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            layout: &bind_group_layout,
            bindings: &[],
        });

We are currently getting this validation error:

ERROR gfx_backend_vulkan >
VALIDATION [VUID-VkDescriptorPoolCreateInfo-poolSizeCount-arraylength (0)] : vkCreateDescriptorPool: parameter pCreateInfo->poolSizeCount must be greater than 0. The Vulkan spec states: poolSizeCount must be greater than 0 (https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html#VUID-VkDescriptorPoolCreateInfo-poolSizeCount-arraylength)
object info: (type: UNKNOWN, hndl: 0)

Not sure yet if it's to be addressed at our level or in rendy-descriptor (cc @omni-viral ).

[GabrielMajeri]

Where should this be validated in the end? Here, in wgpu-rs, somewhere else?

[kvark]

I'm thinking it should be handled in gfx-descriptor

[cwfitzgerald]

Should test if this is still an issue under gpu-descriptor

[kvark]

Fixed in gpu-descriptor now