[9.18] chg: pkg: Update requirements for system test suite

Python 3.10 or newer is now required for running the system test suite. The required python packages and their version requirements are now tracked in `bin/tests/system/requirements.txt`.

Support for pytest 9.0.0 has been added its minimum supported version has been raised to 7.0.0. The minimum supported dnspython version has been raised to 2.3.0.

Closes #5690

Closes #5614

Backport of MR !11415

Merge branch 'backport-nicki/pytest-9-compat-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!11470