Refactored the Vulkan::Sampler class

Refactored the Vulkan::Sampler class

> Removed the PIMPL pattern
> Sampler can now only be immutable
> Samplers should be unique and be created at initialization
> Sampler creation logic moved to the Vulkan::Graphics class
> Added the method AddSampler to the Vulkan::Graphics class
> Sampler lifetime is now managed by the Vulkan::Graphics class

Change-Id: Ifa4a9364e3dc2cf483e694648e4b03f35b689398