[9.16] chg:test: Disable too-many/too-few pylint checks

Enforcing pylint standards and default for our test code seems
counter-productive. Since most of the newly added code are tests or is
test-related, encountering these checks rarely make us refactor the code
in other ways and we just disable these checks individually. Code that
is too complex or convoluted will be pointed out in reviews anyways.

(cherry picked from commit f7319a38cf277c2140f0ed7ab46fd616b9322587)

Backport of MR !9626

Merge branch 'backport-nicki/pylint-disable-too-few-too-many-checks-9.16' into 'bind-9.16'

See merge request isc-projects/bind9!9806