We have to double-check that providers work and can be tested locally when installing airflow in a local virtualenv.

After we've changed to separate providers and core package, pip install . will not install those packages, but with local -e it will likely work as providers packages are in the same folder.

We still need to check how local virtualenv work when we install without -e though.

Most likely solution will be dynamic selection of packages in setup.py based on the fact whether you are installing airflow from packages or sources.

This is connected with #11464