This makes wide line supported on MacOS and other implementation that
does not support wide line by default.
This workaround works for all Line types but only if using one of the 5
default shaders.
The workaround is completely isolated and invisible to the outside. It has
no side effect.
Note: This does not affect the GPUBatch drawing.
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
