D9054 did multiple consecutive `immBegin()`/`immEnd()` draw calls to draw
multiple lines at varying thickness. This would only work for the first line,
then they'd all get a 1px thickness (at least on macOS).
Issue was that `wide_line_workaround_end()` called `immBindShader()` directly
to restore the old shader (which the workaround overrides). However this
doesn't set `imm->builtin_shader_bound` which has to be done for the workaround
to work on the next `immBegin()` call. Instead `immBindBuiltinProgram()` can be
called.
Differential Revision: https://developer.blender.org/D10520
Reviewed by: Clément Foucault
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
