chore: Update Docker build and test workflows

chore: Update Docker build and test workflows This commit makes the following changes: - **docker-buildx.yml**: - Changes the `push` trigger to `workflow_run` to only build Docker images after the "Test Drupal Installation" workflow succeeds. - Adds a condition to the `buildx` job to prevent it from running if the workflow was triggered by `workflow_run` and the previous workflow failed. - **test-drupal.yml**: - Replaces `docker-compose` with `docker compose` for consistency and to leverage the `docker-compose-plugin`. - Adds a step to install `docker-compose-plugin` to ensure compatibility.