ci: use git submodules for (securely) using third party Github Actions (#12709)

* Use git submodules for (securely) using third party Github Actions

List of repositories added as submodules:

EndBug/latest-tag@latest
morrisoncole/pr-lint-action@v1.4.1
trilom/file-changes-action@v1.2.4
styfle/cancel-workflow-action@0.6.0
apache-superset/cached-dependencies@b90713b
unsplash/comment-on-pr@v1.2.0

.github/workflows/superset-python-presto-hive.yml

@@ -46,7 +46,11 @@ jobs:
         ports:
           - 16379:6379
     steps:
-      - uses: actions/checkout@v2
+      - name: "Checkout ${{ github.ref }} ( ${{ github.sha }} )"
+        uses: actions/checkout@v2
+        with:
+          persist-credentials: false
+          submodules: recursive
       - name: Setup Python
         uses: actions/setup-python@v2
         with:
@@ -97,7 +101,11 @@ jobs:
         ports:
           - 16379:6379
     steps:
-      - uses: actions/checkout@v2
+      - name: "Checkout ${{ github.ref }} ( ${{ github.sha }} )"
+        uses: actions/checkout@v2
+        with:
+          persist-credentials: false
+          submodules: recursive
       - name: Create csv upload directory
         run: sudo mkdir -p /tmp/.superset/uploads
       - name: Give write access to the csv upload directory