With C++20 the custom container PS:span, which was a backport of
std::span is no longer needed.
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
Make include-what-you-use happy with some files in source/renderer and
fix what needs to be fixed.
Ref: #8086
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>