Align Flink's UC4 implementation with Kafka Streams implementation

The latest version of our Kafka Streams implementation contains a feedback loop and possibly also some other adjustments, which should be ported to our Flink implementation as well.

See also:

• https://www.sciencedirect.com/science/article/pii/S2214579621000265
• https://link.springer.com/article/10.1007/s41688-020-00041-3