(MODULES-11418) Add unit test resuable workflows

This commit switches the GitHub Actions workflows for unit tests
over to using the reusable workflows in
puppetlabs/phoenix-github-actions.

Author: mhashizume

.github/workflows/unit_tests.yaml

@@ -0,0 +1,16 @@
+---
+name: Unit Tests
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+
+jobs:
+  Nightly:
+    uses: "puppetlabs/phoenix-github-actions/.github/workflows/unit_tests_with_nightly_puppet_gem.yaml@main"
+  
+  Released:
+    uses: "puppetlabs/phoenix-github-actions/.github/workflows/unit_tests_with_released_puppet_gem.yaml@main"