vulkan: pass VK_LAYER_FUNCTION_DATA_CALLBACK to layers

VK_LAYER_FUNCTION_DATA_CALLBACK effectively allows us to pass
driver::SetDataInternal to layers.  It will be called on handles of
potentially unknown types.  Add two internal types

  VK_DEFINE_HANDLE(InstanceDispatchable)
  VK_DEFINE_HANDLE(DeviceDispatchable)

in driver namespace for type safety.

Bug: 28015368
Change-Id: I7389829a7d8c374197cd7046973777b49e436961