Vulkan Sampler implementation

Vulkan Sampler implementation

The Vulkan sampler is simply a state, similar to the existing
sw::Sampler::State(), which will eventually be used by the
texture sampling code.

Bug b/119823006

Change-Id: Ib2f09683f82dbf5b5aacde1555ee850c76cda9e2
Reviewed-on: https://swiftshader-review.googlesource.com/c/22728
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>