v0.12.1

What's Changed

• [doc] update quick start doc by @huangzhiran in #541
• [stresstest] update stress test logic by @huangzhiran in #542
• [doc] update readme&developer_guide&operator_guide doc by @huangzhiran in #543
• [vm] delete vm intance cache by @huangzhiran in #544

Full Changelog: v0.12.0...v0.12.1