fix(workflows): enable submodules, remove upstream cachix action

[eum3l]

This PR fixes the broken workflows.
Versions after Nix v2.18.x seem to have a parsing bug (NixOS/nix#6633) with flakerefs.
Since cachix/install-nix-action uses v2.22.1, putting a # at the end of the flakeref fixes the submodule argument. Going back to v.2.18.x would also be an option.
The cargo-build.yml workflow now executes cargo build in a devShell with the dependencies of the package. This fixes outdated syntax.
I've also removed the workflow for the upstream cache.
If you want to add one for this project see Cachix and Nix CI with GitHub Actions.
The plugins are now also getting built with gtk4.
cargo-bump has been removed from cargo-update.yml, as it is no longer maintained and doesn't support workspaces.

[bzglve]

Awesome, thanks a lot <3
But I need to be sure
I've recently added glib schema as app state and moved default settings to /etc/xdg (XDG_CONFIG_DIRS)
Doesn't nix need to copy that like in install.sh do?

[eum3l]

Awesome, thanks a lot <3 But I need to be sure I've recently added glib schema as app state and moved default settings to /etc/xdg (XDG_CONFIG_DIRS) Doesn't nix need to copy that like in install.sh do?

I fixed those with a refactor on eum3l/anyrun/fix-share.
Unfortunately it is based on this PR.
I'll make the new one, when this has been merged. :)

[bzglve]

I'm looking forward to it
Thanks a lot