ci: update test scripts to use install-poetry.py and cleanup release workflow

[abn]

This change also fixes python 3.10 failures.

[abn]

THe new 3.10 failures are due to missing setuptools in the project virtual environment. Since new versions of poetry drops pip and setuptools from project environments (python-poetry/poetry#2826), we have an issue with adding it as a development dependency (which is the right fix) in that adding via poetry@master will lead to all existing versions to fail as they mark setuptools and unsafe, leading to resolution errors.

@sdispater I wonder if this makes a good case for pyproject.toml allowing a configuration for min-poetry similar to what tox does.