Vulkan resource lifecycle management

Vulkan resource lifecycle management

For Vulkan implementation of graphics resources:
  Added discard queue, that's cleaned down during Flush().

Added ResourceWithDeleter as a secondary interface on top of ResourceBase, to allow
Program/Pipeline to inherit solely from ResourceBase, and not have to utilize the
same resource deleters that the main graphics objects require.

Removed VkResource inheritance completely from Impl classes.
Kept VkResource as VkSharedResource, as we may still use this on RenderPassImpl

All Impl classes now have a public Destroy method which is called from their
destructor, but may also be called earlier if needed. Note, CommandBuffers should
not be deleted directly, but instead returned to the command pool for re-use.

Implemented owned containers for some Impl objects using
std::unique_ptr. Framebuffer owns it's attachments, Swapchain owns
it's framebuffers.

Change-Id: I651ed4d041cd2fb3e7698304eeede66625031945