Update GE injection script for Develocity rename

- Rename all env vars expected by init-script: `s/GRADLE_ENTERPRISE/DEVELOCITY`
- Update README for changes
- Use `Develocity` consistently in tests

.github/workflows/integ-test-inject-develocity.yml

@@ -0,0 +1,60 @@
+name: Test develocity injection
+
+on:
+  workflow_call:
+    inputs:
+      cache-key-prefix:
+        type: string
+      runner-os:
+        type: string
+        default: '["ubuntu-latest", "windows-latest", "macos-latest"]'
+      download-dist:
+        type: boolean
+        default: false
+    secrets:
+      DEVELOCITY_ACCESS_KEY:
+        required: true
+
+env:
+  DOWNLOAD_DIST: ${{ inputs.download-dist }}
+  GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX: provision-gradle-versions-${{ inputs.cache-key-prefix }}
+  GRADLE_BUILD_ACTION_CACHE_DEBUG_ENABLED: true
+  DEVELOCITY_INJECTION_ENABLED: true
+  DEVELOCITY_URL: https://ge.solutions-team.gradle.com
+  DEVELOCITY_PLUGIN_VERSION: 3.16.1
+  DEVELOCITY_CCUD_PLUGIN_VERSION: 1.12.1
+  GRADLE_ENTERPRISE_ACCESS_KEY: ${{ secrets.DEVELOCITY_ACCESS_KEY }} # This env var has not (yet) been renamed/aliased in GE plugin 3.16.1
+
+jobs:
+  inject-develocity:
+    strategy:
+      matrix:
+        gradle: [current, 7.6.2, 6.9.4, 5.6.4]
+        os: ${{fromJSON(inputs.runner-os)}}
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v4
+    - name: Download distribution if required
+      uses: ./.github/actions/download-dist
+    - name: Setup Java
+      uses: actions/setup-java@v4
+      with:
+        distribution: temurin
+        java-version: 8
+    - name: Setup Gradle
+      id: setup-gradle
+      uses: ./
+      with:
+        cache-read-only: false # For testing, allow writing cache entries on non-default branches
+        gradle-version: ${{ matrix.gradle }}
+    - name: Run Gradle build
+      id: gradle
+      working-directory: .github/workflow-samples/no-ge
+      run: gradle help
+    - name: Check Build Scan url
+      if: ${{ !steps.gradle.outputs.build-scan-url }}
+      uses: actions/github-script@v7
+      with:
+        script: |
+          core.setFailed('No Build Scan detected')