Set vllm as default llm serving, and add related docker compose files, readmes, and test scripts. Issue: https://github.com/opea-project/GenAIExamples/issues/1436 Signed-off-by: letonghan <letong.han@intel.com> Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>