Release library in Flink independent version way

[novakov-alexey]

Context: currently this library is released as 3 separate published JARs for the last 3 Apache Flink versions. For example:

• 1.18.1_1.2.0
• 1.19.1_1.2.0
• 1.20.0_1.2.0

Such approach make the release process quite slow, because it requires 3 bundles to be published to the Sonatype repository.
Also, it forces a user to think which version to select based on his Flink version used in a project. Not a big deal, but why bother with this?

Proposal:

1. Build and publish a single JAR only without Flink version prepended.

2. In order to keep Flink compatibility guarantees, still run sbt tests in GH Action for the last 3 Flink version as it is now.
   In the result, this library gets verified across different Flink versions, but will have single version schema, which simplifies dependency management process for the users.

Caveats

1. What if build fails in one or two Flink version while it is still successful for one of the versions. This may happen in future with Flink 2.0 and Flink 1.x