python.testing.cwd not respected for python rewrite

[eleanorjboyd]

while on the rewrite ("python.experiments.optInto": ["pythonTestAdapter"]), the following setting python.testing.cwd is not respected. It is not considered in the code and so it must be fix to respect this setting when provided.

[eleanorjboyd]

discovered during testing: #20711

[eleanorjboyd]

verification steps:

1. go to this repo: https://github.com/eleanorjboyd/inc_dec_example_repo/tree/main/inc_dec_example_test_suite clone it and go int othe inc_dec_example_test_suite folder
2. add in a value for settings.testing.cwd so it points at a subdirectory of your workspace (like outer_nested_folder)
3. in the command line do python -m pip install pytest then reload window
4. click on the test explorer to run tests. If it is asking you to configure tests pick pytest then default values
5. Now check that when you look at the test explorer there are no errors and the root folder you see is the one you put in as settings.testing.cwd