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

diff --cc Documentation/meson.build
Simple merge

diff --cc meson.build
Simple merge