* Remove use of getClass in secondary constructors
As this is not allowed anymore on newer versions of scala, and likely
didn't work correctly in the past either
This might make selecting unique actor system names for test
actor systems a bit less reliable, but that didn't seem to be
critical anyway.
Thanks to @som-snytt for the heads-up and initial implementation
in #28353
* Avoid AkkaSpec.getCallerName in MultiNodeClusterShardingConfig
* StreamSpec can be abstract
* Use more sophisticated test class name logic
* scalafmt
