Full rewrite of devshell

migrates pre-commit to cachix's pre-commit-hooks

adds a ton of new hooks:
- check-added-large-files
- check-case-conflicts
- check-json
- check-merge-conflicts
- detect-private-keys
- fmt-check
- nil
- no-commit-to-branch
- statix (disabled for now)

migrates devshell to new devshells, set up modularly to have separate
functionality for sops, pre-commit-hooks, and our custom packages

Signed-off-by: ahuston-0 <aliceghuston@gmail.com>

shell.nix

@@ -0,0 +1,40 @@
+{
+  forEachSystem,
+  nixpkgs,
+  checks,
+  sops-nix,
+  ...
+}:
+
+forEachSystem (
+  system:
+  let
+    pkgs = nixpkgs.legacyPackages.${system};
+    pre-commit = pkgs.mkShell {
+      inherit (checks.${system}.pre-commit-check) shellHook;
+      buildInputs = checks.${system}.pre-commit-check.enabledPackages;
+    };
+    sops = pkgs.mkShell {
+      sopsPGPKeyDirs = [ "./keys" ];
+      packages = [
+        pkgs.sops
+        sops-nix.packages.${system}.sops-import-keys-hook
+      ];
+    };
+    rad-dev = pkgs.mkShell {
+      packages = with pkgs; [
+        deadnix
+        pre-commit
+      ];
+    };
+  in
+  {
+    default = pkgs.mkShell {
+      inputsFrom = [
+        pre-commit
+        rad-dev
+        sops
+      ];
+    };
+  }
+)