Better support for Java's pattern matching.

[He-Pin]

On Java 17, we should try to use the new pattern matching on Java instead of the ReceiveBuidler or etc things, maybe we should add some new classes for better integration.

[pjfanning]

We have a section in the Pekko docs about Java 21 switch.
https://pekko.apache.org/docs/pekko/current/actors.html#receive-messages (switch to Java code instead to Scala).

[He-Pin]

Yes, but it currently extends the UntypedAbstractActor, which should be an Abstract*Actor, with something like onMessageReceved or onMessage etc

[He-Pin]

#2379