akka-stream compiling on Scala 3 (#30324)

Changes:
* Private constructor for case class means private apply in Scala 3
* Logger class with Any instead of wildcard where needed
* Explicit import of internal implicit conversion import SinkToCompletionStage
* Hopefully source and binary compatible Scala 3 signature for GraphApply.create methods
* ZipLatestWith leaking private type
* Auto apply-to-lambda made explicit
* Internal async callback event class covariant
* Hub leaking private type
* Remove cycles in stream Buffer classes
* Avoid cyclic import in ResizableMultiReaderRingBuffer
* Safe cast of Subscribers
* Explicit import of internal implicit conversion SourceToCompletionStage
* Ambigous field name and method
* recover delegates using PF from javadsl not inferred, made explicit
* TcpStage completing promise with wrong type
* Collect aggregator empty value cannot be underscore with type ascription
* Some type alias shenanigans in QueueSink removed
* Explicit type on effectiveMaximumBurst in Throttle
* Override method return type not inferred in GraphInterpreter
* MutableCollectorState.accumulated getter got wrong type somehow
* TLS actor fallback case only applicable to null
* Some internal unchecked pattern matching removed
* Ok that createGraph is not present in Java API
* Separate impl per language for implicit actor system apply

akka-stream/src/main/scala/akka/stream/impl/Throttle.scala

@@ -40,7 +40,7 @@ import akka.util.NanoTimeTokenBucket
   private val nanosBetweenTokens = per.toNanos / cost
   // 100 ms is a realistic minimum between tokens, otherwise the maximumBurst is adjusted
   // to be able to support higher rates
-  val effectiveMaximumBurst =
+  val effectiveMaximumBurst: Long =
     if (maximumBurst == Throttle.AutomaticMaximumBurst) math.max(1, ((100 * 1000 * 1000) / nanosBetweenTokens))
     else maximumBurst
   require(!(mode == ThrottleMode.Enforcing && effectiveMaximumBurst < 0), "maximumBurst must be > 0 in Enforcing mode")