fs2-kafka v3.0.0-M4

This is the first milestone release of fs2-kafka following the release of 2.0.0. (We have previously released v3.0.0-M1 through v3.0.0-M3 but these became the 2.x series following a change in our roadmap.)

This is the first release of fs2-kafka to use version 3.0.0 of the Apache Kafka client library, which is not binary-compatible with previous versions. It is available for Scala 2.13 and Scala 3.1; Scala 2.12 has been dropped for the 3.x series but will continue to be supported in the 1.x and 2.x series.