refactor(update-script): Switch from nvfetcher to nix-update

pkgs/update.nu

@@ -0,0 +1,23 @@
+use std/log
+
+let packages_with_updatescript = (
+  nix flake show --json
+  | from json
+  | $in.packages.x86_64-linux
+  | columns
+  | filter {|p| nix eval $'.#($p)' --apply 'builtins.hasAttr "updateScript"' | $in == 'true' }
+)
+
+for $package in $packages_with_updatescript {
+  log info $'Updating ($package)'
+  nix run $'.#($package).updateScript'
+}
+
+log info 'Committing changes'
+
+try {
+  git add pkgs
+  git commit -m 'update(pkgs): Update sources of all downstream packages'
+} catch {
+  log warning 'No changes to commit'
+}