=doc Describe how to use microKernel with sbt-native-packager

(cherry picked from commit 6a79ad1287fb776eac1cac07a8a45dc0b597cede)

Conflicts:
	project/plugins.sbt
=doc #13043 Adding section on testing parent-child relationships
!clu #15042 useRole restriction on local node is now respected
This is an API breaking change if someone implemented their own Routers.
The change is required because the router must know if the local routees
should be started or not so it has to check the roles of the cluster
member (the local one). We could delay this decision of starting local
routees, but that would allow messages to be dead-letter-ed (bad).
Merge pull request #15822 from ktoso/clu-useRole-ignored-local-ktoso

useRole ignored on local, because routers unaware of roles locally
=con #15788 Harden ClusterShardingSpec
Merge pull request #16192 from ktoso/doc-push-over-finish-line-actor-child-testing-ktoso

=doc #13043 Adding section on testing parent-child relationships
Merge pull request #16173 from akka/wip-native-packager-patriknw

=doc Describe how to use microKernel with sbt-native-packager
Merge pull request #16202 from akka/wip-15788-harden-ClusterShardingSpec-patriknw

=con #15788 Harden ClusterShardingSpec
=per #16009 Serialize SnapshotHeader without Java serialization

* it is backwards compatible, i.e. it can read old snapshots

(cherry picked from commit 690905eac9619da91d7b1fcbc633d1fa2e411ee7)

Conflicts:
	akka-persistence/src/test/scala/akka/persistence/serialization/SerializerSpec.scala
=doc #16198 FSM extends Actor, not depends on it

The documentation incorrectly stated that FSM uses self type references
to depend on Actor, but it’s false, FSM directly extends Actor.
Merge pull request #16211 from akka/wip-16009-snapshot-header-serializer-master-patriknw

=per #16009 Serialize SnapshotHeader without Java serialization (for validation)
Merge pull request #16213 from kosii/kosii/fsm_docs_fix_#16198

=doc #16198 FSM extends Actor, not depends on it