This is part of the Vulkan backend task T68990.
This is mostly a cleanup, however, there is a small change:
We don't use a special Vertex Array binding function for Immediate
anymore and just reuse the one for batches.
This might create a bit more state changes but this could be fixed
easily if it causes perf regression.
# Conflicts:
# source/blender/gpu/intern/gpu_context.cc
