Meson: some more improvements
Meson: Pass all dependencies to gnome.generate_gir() This is needed when for example gtk4 is built as subproject so it needs to find gtk-4.git from build directory.
Meson: There is no reason for gtksource_dep to be different with MSVC
meson: Use summary() instead of custom formatted string
Bump glib dependency to 2.66 This is the version required by gtk4. This fix meson error on distro like Ubuntu 20.04 LTS that has glib 2.64 but not gtk4, so the configuration of gtk4 subproject fails because of too old glib version found and it cannot fallback to glib subproject any more because gtksourceview is using the system dependency already.