Switch anonymized replayer test to use pytest parametrization
This allows us to only read the kafka topics once instead of twice in the same tests, which is apparently a hard thing to do in a way compatible with both confluent-kafka 1.5 and 1.6.
Test Plan
tested in tox with both confluent-kafka 1.5.0 and 1.6.0
Migrated from D5085 (view on Phabricator)