Backport bitcoin#11817: [tests] Change feature_csv_activation.py to use BitcoinTestFramework (#3278)
Backport bitcoin#11817: [tests] Change feature_csv_activation.py to use BitcoinTestFramework (#3278)

* [tests] fix flake8 nits in feature_csv_activation.py

* [tests] improve logging in feature_csv_activation.py

* [tests] Remove nested loops from feature_csv_activation.py

Makes the test a lot clearer.

* [tests] Move utility functions in feature_csv_activation.py out of class.

* [tests] Change feature_csv_activation.py to use BitcoinTestFramework

* Few import fixes

Co-authored-by: John Newbery <c5f687098c6c72419cd857e4d3b02d3ecaae7cb1@gmail.com>

UdjinM6/dash,UdjinM6/dash,UdjinM6/dash,dashpay/dash,thelazier/dash,dashpay/dash,thelazier/dash,dashpay/dash,thelazier/dash,dashpay/dash,UdjinM6/dash,UdjinM6/dash,thelazier/dash,thelazier/dash,dashpay/dash