Use Environment variable in .properties file

The Python Client picks most of its configuration like `streamName` from `.properties` file. Is there a way to pick them from environment variables?

Start by locating how the Python Client reads configuration from the .properties file, especially the streamName setting. Check whether environment variables are already supported elsewhere and identify the expected precedence between both sources. Done means configuration values can be supplied from environment variables with documented behavior and coverage for the relevant settings.

Written by the indexing model from the issue text.