layers: Combine Destroy{Non,}DispatchableObject
layers: Combine Destroy{Non,}DispatchableObject

These did exactly the same thing, except for the slight wrinkle of
needing to cast to uint64_t & in the nondispatchable case to account for
MSVC crankiness. We can just do that always.

Signed-off-by: Chris Forbes <c3279c50043e18e9442c1ae071cafa0e7a4ca967@google.com>

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers