DS-970: Add Magic Nix Cache and other workflow changes (#569)

* DS-970: Add Magic Nix Cache and other workflow changes

 An assortment of GitHub Workflow changes, potentially including:

- Enable DeterminateSystems/magic-nix-cache-action@main
- Reference all DeterminateSystems actions via @main
- Make update.yaml consistent across repos
- Remove unnecessary github-token: from nix-installer-action
- Update actions/checkout@v2 to actions/checkout@v3

* ci: clearly name steps in update.yml

.github/workflows/ci.yml

@@ -12,13 +12,13 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Check Nixpkgs input
-        uses: DeterminateSystems/flake-checker-action@v4
+        uses: DeterminateSystems/flake-checker-action@main
         with:
           fail-mode: true
           check-outdated: false # PRs shouldn't fail because main's nixpkgs is out of date
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@main
-      - uses: DeterminateSystems/magic-nix-cache-action@v1
+      - uses: DeterminateSystems/magic-nix-cache-action@main
       - name: Check rustfmt
         run: nix develop --command check-rustfmt
       - name: Check Spelling

.github/workflows/update.yml

@@ -6,13 +6,15 @@ on:
 
 jobs:
   lockfile:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
-      - name: Checkout repository
+      - name: Checkout
         uses: actions/checkout@v3
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@main
-        with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
+      - name: Enable magic Nix cache
+        uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: Check flake
+        uses: DeterminateSystems/flake-checker-action@main
       - name: Update flake.lock
-        uses: DeterminateSystems/update-flake-lock@v16
+        uses: DeterminateSystems/update-flake-lock@main