build: inline external Github Actions to unblock CI (#12241)

* build: inline cached-dependencies to unblock CI

* Run E2E on pull_request on;y

* Inline all external actions

* Checkout needed for internal actions

Also fixes pre-commit

* Add missing files

.github/workflows/superset-docs.yml

@@ -13,10 +13,6 @@ jobs:
     name: build
     runs-on: ubuntu-18.04
     steps:
-      - name: Cancel Previous Runs
-        uses: styfle/cancel-workflow-action@0.6.0
-        with:
-          access_token: ${{ github.token }}
       - name: Checkout code
         uses: actions/checkout@v2
       - name: npm install