* Move out VulkanBenchmark and DrawBenchmark classes to their own
  hpp/cpps.
* Move out ClearImageBenchmark and TriangleBenchmark classes and tests
  to their own cpps.
* Add non-template DrawBenchmark::addVertexBuffer that takes the size of
  the vertex type. This allows for the implementation to be moved to the
  cpp file, keeping the header light and easy to understand.

Bug: b/176981107
Change-Id: I657bd112c5523aa56dc5617082d6744b9edac03a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52130
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>