Python prerequisites for make e2e-test

make e2e-test also requires a test database and, for some service tests, libgit2. See backend/test/Readme.md for the full local E2E test flow.

For the Python plugin tests to run properly, the following steps must be taken:

1. The following packages are required for Ubuntu: libffi-dev default-libmysqlclient-dev libpq-dev
2. python3.9 is required by the time of this document.
   • Try deadsnakes if you are using Ubuntu 22.04 or above, the python3.9-dev is required.
   • Use virtualenv if you are having multiple python versions. virtualenv -p python3.9 path/to/venv and source path/to/venv/bin/activate.sh should do the trick
3. both mysql-client and postgresql are required.
   • postgresql is required for psycopg2 to work
4. poetry is required.
   • run cd backend/python/pydevlake && poetry install
   • run cd backend/python/plugins/azuredevops && poetry install
5. sqlalchemy won't work with localhost in the database connection string, use 127.0.0.1 instead