VkPipeline simple implementation

VkPipeline simple implementation

Added a few class members and adjusted the VkPipeline constructor
to extract basic parameters which will be used for rendering, like:
- Basic sw::Context parameters
- Scissor
- Viewport
- BlendConstants

Note: sw::Context should eventually be replaced by VkPipeline and be
      used directly by sw::Renderer once all existing OpenGL ES 3.0
      has been converted from VkPipeline.

(Chris: rebase + build system fixes for CMake path)

Change-Id: I7e7a9ff3c768da8e8c1e9461e140af4986429602
Reviewed-on: https://swiftshader-review.googlesource.com/c/22613
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Corentin Wallez <cwallez@google.com>