Combine all integTest workflows into 2 workflow runs

- Workflow to run all integTest workflows, allowing use of prior cache entries
- Workflow that starts with empty cache

Both of these use workflow_call to combine the existing workflows.

.github/workflows/demo-pr-build-scan-comment.yml

@@ -0,0 +1,27 @@
+name: Add a build scan comment to PR
+on:
+  pull_request:
+    types: [assigned, review_requested]
+jobs:
+  gradle:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout project sources
+      uses: actions/checkout@v2
+    - name: Setup Gradle
+      uses: ./
+    - name: Run build with Gradle wrapper
+      id: gradle
+      working-directory: .github/workflow-samples/kotlin-dsl
+      run: ./gradlew build --scan
+    - name: "Add build scan URL as PR comment"
+      uses: actions/github-script@v5
+      with:
+        github-token: ${{secrets.GITHUB_TOKEN}}
+        script: |
+          github.rest.issues.createComment({
+            issue_number: context.issue.number,
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            body: 'PR ready for review: ${{ steps.gradle.outputs.build-scan-url }}'
+          })