Follow-up for #4454. based on that branch, merge after.
Uses the offline_bot in all the *WithoutRequest tests and fixes the very few places where requests where still being made.
The check for enforcing offline_bot is now configured to run only on GitHub and only in one of the several test matrix runs. IMO this should suffice and avoids running additional if-checks on every single test function unnecessarily.

By cutting of the internet connection in the fixtures

…uest_tests

LGTM!