WIP: Update GNOME stack

I've been working with @marvil07 on getting podcasts packaged, and part of that means updating the GNOME/GTK stack.

I'm sharing this preliminary WIP branch to avoid duplicating efforts with anyone else working on this.

There are still a couple more crates that need updating before I can make it to glib proper. I'm currently stuck in syn because of a bug in debcargo (see debcargo#37 (closed)).

I was able to progress beyond syn by patching out the test feature since it was broken anyway because of a different bug in cargo (https://github.com/rust-lang/cargo/issues/7180).

I'm happy to keep working on this and correct any oversight, let me know if this is heading in the right direction. Please excuse any crude mistakes 🤡 🎺 😆