Bump node environment to 16.x

- Bump setup-node action to v2.
- Use composite actions to reuse same setting. This is preferred over
  reusable templates because reusable templates are on job-level but
  setting up node should be a step.

.github/actions/setup-node/action.yml

@@ -0,0 +1,8 @@
+runs:
+  using: composite
+  steps:
+    -
+      name: Setup node
+      uses: actions/setup-node@v2
+      with:
+        node-version: 16.x