Unit Testing: Multiple perper agents in a single process

When writing integration tests using nunit (xunit) the runners execute all test of a single assembly into a single process. This require the ability to sequentially initialize / destroy new perper agents into the same process.

Workaround: invoke separate test runner for every test (see https://github.com/comrade-coop/apocryph-dao-bot/blob/master/.github/workflows/dotnet.yml)