remove copy of mdspan reference implementation; instead download a version on-demand.

.gitlab-ci.yml

pyproject.toml

tests/generator_scripts/.gitignore

...pan/include/experimental/__p0009_bits/compressed_pair.hpp

.../deps/mdspan/include/experimental/__p0009_bits/config.hpp

...an/include/experimental/__p0009_bits/default_accessor.hpp

...span/include/experimental/__p0009_bits/dynamic_extent.hpp

...deps/mdspan/include/experimental/__p0009_bits/extents.hpp

...dspan/include/experimental/__p0009_bits/full_extent_t.hpp

.../mdspan/include/experimental/__p0009_bits/layout_left.hpp

...mdspan/include/experimental/__p0009_bits/layout_right.hpp

...dspan/include/experimental/__p0009_bits/layout_stride.hpp

.../deps/mdspan/include/experimental/__p0009_bits/macros.hpp

.../deps/mdspan/include/experimental/__p0009_bits/mdspan.hpp

...n/include/experimental/__p0009_bits/no_unique_address.hpp

...pan/include/experimental/__p0009_bits/trait_backports.hpp

...ps/mdspan/include/experimental/__p0009_bits/type_list.hpp

...deps/mdspan/include/experimental/__p1684_bits/mdarray.hpp

...dspan/include/experimental/__p2630_bits/strided_slice.hpp

...ps/mdspan/include/experimental/__p2630_bits/submdspan.hpp