meson: Add macOS libtool versioning for ABI compatibility

With this, the compatibility version and current version values in macOS and iOS dylibs will match the values set by Autotools.

See: https://github.com/mesonbuild/meson/issues/1451

WIP because this should only be merged after https://github.com/mesonbuild/meson/pull/4095 is merged and Meson 0.48 has been released. I'm filing it now so that we can track it as a blocker for a Meson-only release.

Alternatively, we could add this kwarg without changing the required Meson version, because the kwarg will just get ignored (with a warning).