[python-flask] Move `test` directory out of code directory

Created by: alfechner

In my org we want the structure of Python packages to be consistent. I try to adjust the output of the python-flask generator.

After generating I end up with a directory structure like this:

/my_service
|_ controllers
|_ models
|_ ...
|_ test

I'd like to generate the test directory outside of my_service and call it tests:

/my_service
|_ controllers
|_ models
|_ ...
/tests

Is that possible?

6.0.1