pyinfra 3.8.0 brings full semver, API decoupling, and key security fixes

pyinfra 3.8.0 adopts full semantic versioning and decouples its core API from click via pluggable output functions. This release includes expanded quoting for user inputs and untrusted values to address command injection risks. New facts and operations target docker support, along with security and usability enhancements. The update also brings extensive bug fixes and documentation improvements.