ci: use setup-gradle action to provision gradle on CI

This action has support for retrying on network failure and also
supports Github's Action toolcache.

Fixes servo#34600

.github/workflows/android.yml

@@ -79,6 +79,14 @@ jobs:
         id: setup-ndk
         with:
           ndk-version: r26c
+      - name: Install gradle
+        uses: gradle/actions/setup-gradle@v4
+      - name: Ensure gradle is downloaded
+        run: |
+            for i in {1..5}; do
+              ./gradlew --version && break || { echo "Downloading gradle failed (attempt $i)." && sleep $((2 ** $i)); };
+            done
+        working-directory: ./support/android/apk/
       - name: Setup Key Store for APK Signing
         env:
           KEYSTORE_BASE64: ${{ secrets.APK_KEYSTORE_BASE64 }}