use nix caching and docker caching in CI

Also bumps tailscale version to trigger build and fixes a CLI test
that had the wrong capitalisation

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

cmd/gh-action-integration-generator/main.go

@@ -39,6 +39,11 @@ jobs:
         with:
           fetch-depth: 2
 
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - uses: satackey/action-docker-layer-caching@main
+        continue-on-error: true
+
       - name: Get changed files
         id: changed-files
         uses: tj-actions/changed-files@v34
@@ -50,9 +55,6 @@ jobs:
             integration_test/
             config-example.yaml
 
-      - uses: cachix/install-nix-action@v18
-        if: {{ "${{ env.ACT }}" }} || steps.changed-files.outputs.any_changed == 'true'
-
       - name: Run general integration tests
         if: steps.changed-files.outputs.any_changed == 'true'
         run: |