nix: Use nix-systems to provide the needed systems as flake inputs

[xtrm-en]

This change allows flake consumers to override the systems input to provide only the necessary output, instead of every system possible. See the nix-systems project.

$ nix flake show --override-input systems github:nix-systems/x86_64-linux
• Updated input 'systems':
    'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e?narHash=sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768%3D' (2023-04-09)
  → 'github:nix-systems/x86_64-linux/2ecfcac5e15790ba6ce360ceccddb15ad16d08a8?narHash=sha256-Gtqg8b/v49BFDpDetjclCYXm8mAnTrUzR0JnE2nv5aw%3D' (2023-04-08)
git+file:///home/x/Work/@me/zed
├───devShells
│   └───x86_64-linux
│       └───default: development environment 'nix-shell'
├───formatter
│   └───x86_64-linux: package 'nixfmt-unstable-2024-11-26'
├───overlays
│   ├───default: Nixpkgs overlay
│   ├───rust-overlay: Nixpkgs overlay
│   ├───rust-toolchain: Nixpkgs overlay
│   └───zed-editor: Nixpkgs overlay
└───packages
    └───x86_64-linux
        ├───default: package 'zed-editor-nightly'
        └───zed-editor: package 'zed-editor-nightly'

This PR also updates the flake inputs to their latest versions.

Release Notes:

• N/A

[mikayla-maki]

It seems that this pattern is somewhat controversial: NixOS/nix#3843 (comment). And I don't think we want to add speculative features to our flake, particularly as not many of us use nix ourselves.

Caveat: I'm not a nix person and I don't know what's going on in y'alls community. Please let me know if this is incorrect :)