[v4.9.2] Adapt deprecated asio API

Added

io_context support and asio API adaptations
Replace io_context::work

Docker images

https://github.com/users/testillano/packages/container/package/h2agent
https://github.com/users/testillano/packages/container/package/h2agent_builder
https://github.com/users/testillano/packages/container/package/h2agent_training

Issues report

Changelog

v4.9.1...v4.9.2