This trait represents a parsed method call with deserialized arguments,
to abstract over call parsing.

Then add new registration builder helpers to register method calls with
a simplified callback which receives parsed arguments, and can
optionally return an async result.

Fixes gtk-rs#1585

Only the ones that can be generated now without requiring any manual
implementations.

Leave it up to the consumer to determine the specific version.

It was not exported at all before.

Fixes gtk-rs#1597

…t_with_closures()

Assume that the invocation is passed as `transfer full` into the
closure.

This workaround is not going to break with future versions of
GLib as fixing the bug was considered a breaking API change.

See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/4427