build: Expose autocleanups unconditionally, start using them

build: Expose autocleanups unconditionally, start using them

I'd like to do this in rpm-ostree at least. Originally I was looking at porting
to `G_DECLARE_FINAL_TYPE` but eh, this is easier for now and won't bump our GLib
dependency which might matter for our embedded users.

For now I just did a few replacements in the `remote` command line. A full port
can come as we do other code cleanups.

This will actually break the flatpak build right now, but
that's easy to fix.  And we concluded in e.g.
https://bugs.freedesktop.org/show_bug.cgi?id=95065#c5
it's a bug for downstream projects to do that.

Closes: #756
Approved by: jlebon