Reporting wrong DescriptorType if Sampler/SampledImage share slot

The `NegativePipelineLayout.DescriptorTypeMismatchNonCombinedImageSampler` in https://github.com/KhronosGroup/Vulkan-ValidationLayers/pull/5900 shows we report the following two errors on the same shader

> Validation Error: [ VUID-VkGraphicsPipelineCreateInfo-layout-07989 ] ... pCreateInfos[0] has a type mismatch for descriptor slot [Set 0 Binding 1] for shader (VK_SHADER_STAGE_FRAGMENT_BIT), uses type **VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE** but expected (**VK_DESCRIPTOR_TYPE_SAMPLER** or **VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER**).

and

> Validation Error: [ VUID-VkGraphicsPipelineCreateInfo-layout-07989 ] ... pCreateInfos[0] has a type mismatch for descriptor slot [Set 0 Binding 1] for shader (VK_SHADER_STAGE_FRAGMENT_BIT), uses type **VK_DESCRIPTOR_TYPE_SAMPLER** but expected (**VK_DESCRIPTOR_TYPE_SAMPLED_IMAGE** or **VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER**).

We should only be suggesting `VK_DESCRIPTOR_TYPE_COMBINED_IMAGE_SAMPLER` as a valid option

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This can be observed in the difference between [GLSL](https://github.com/SaschaWillems/Vulkan/blob/master/shaders/glsl/conservativeraster/fullscreen.frag) and [HLSL](https://github.com/SaschaWillems/Vulkan/blob/master/shaders/hlsl/conservativeraster/fullscreen.frag) where both use (Set 0, Binding 1)