Adjust dockerfile to the latest changes in images from hived

Due to latest changes in hived docker images:
- git was removed, so we no longer require it in dockerfile
  (previously it was required for poetry install and
  poetry dynamic-versioning commands. It was fixed by
  embedded_testnet_instance installing only dev packages
  via the --no-root switch, so it requires already installed clive
  from previous stage)
- need to install libboost-all-dev because wax requires it
- need to install poetry just for the embedded_testnet_instance
  (so we can supplement with dev dependencies only. We also create venv
  by python3-venv instead of poetry now)