Reduce the complexity of VkNonDispatchableHandle

- Simplified VkNonDispatchableHandle as much as possible so
  that it's just a wrapper over a uint64_t
- Centralized casting logic in vkObject.hpp
- Explicitly changed "Cast" to "vk::Cast" to differentiate
  from vk::<object>::Cast
- Moved VkDescriptorSet operators from VulkanPlatform.h to
  VkDescriptorPool.cpp

Bug b/129979580

Change-Id: I4fe5fcfe56029c21594088d274bae862999597ad
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/32928
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
diff --git a/src/Vulkan/VkDescriptorPool.hpp b/src/Vulkan/VkDescriptorPool.hpp
index 731dd01..b363ce1 100644
--- a/src/Vulkan/VkDescriptorPool.hpp
+++ b/src/Vulkan/VkDescriptorPool.hpp
@@ -55,7 +55,7 @@
 
 	static inline DescriptorPool* Cast(VkDescriptorPool object)
 	{
-		return reinterpret_cast<DescriptorPool*>(object.get());
+		return DescriptorPool::Cast(object);
 	}
 
 } // namespace vk