Run the Platform unit tests against latest versions of external services

Currently, the Platform CI relies on fixed versions of MongoDB, PostgreSQL, Elasticsearch, Kafka and Redis for unit tests:

• MongoDB: 4.2.7
• PostgreSQL: 11.7.0
• Elasticsearch: 6.8.6
• Kafka: 2.4.x
• Redis: 5.0.7

Let's align on the latest versions, which we target for the Cloud release (11.x) and the LTS:

• MongoDB 4.4.x
• PostgreSQL 13.x
• Elasticsearch 7.9.2
• Kafka 2.6.x
• Redis 6.0.x