Merge branch 'ps/meson-cleanups'

Meson-based build update. * ps/meson-cleanups: ci: use Meson's new `--slice` option meson: update subproject wrappers meson: fix lookup of shell on MINGW64 meson: clean up unnecessary variables meson: improve summary of auto-detected features meson: stop printing 'https' option twice in our summaries meson: stop discovering native version of Python