Refactor Behat setup to pull Docker images in parallel

Prior to this change, the environment initialization process was sequential, which could lead to longer setup times, exceeding the 5 minute limit.

This change modifies the configuration to pull Docker images in parallel, improving the efficiency of the setup process.

Author: johanib

.github/workflows/stepup-behat.yml

@@ -23,10 +23,14 @@ jobs:
           path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
           restore-keys: ${{ runner.os }}-composer-
-      - name: Init environment
+      - name: Pull images in parallel
         run: |
           cd stepup
           cp .env.test .env
+          ${DOCKER_COMPOSE} config --images | xargs -P 10 -I {} docker pull {}
+      - name: Init environment
+        run: |
+          cd stepup
           cp gateway/surfnet_yubikey.yaml.dist gateway/surfnet_yubikey.yaml
           ${DOCKER_COMPOSE} up -d
       - name: Install composer dependencies on the Behat container