!str #15271 make transform() take a factory instead of Transformer
+ Makes reusing flows safe
+ Adds timerTransform for ops which need TimerTransformer
+ Adds TransformerLike in order to keep transform/timerTransform
  typesafe in respect to the passed in type og Transformer

Resolves #15271
Merge pull request #15725 from ktoso/wip-transformerFactory-ktoso

!str #15271 make transform() take a factory instead of Transformer
=str Move new dsl to scaladsl2 package
=str #15746 Rename flow classes
=str #15026 take drop negative
=str #15026 add some scaladoc backticks
!str #15026 change thunk publisher api to () => Option[T]
Merge pull request #15760 from akka/wip-15026-jason-comments-patriknw

!str #15026 Fix issues pointed out by Jason
=str #15744 Hook-up transform to the AST nodes

* Removed unused parts of the new dsl, such as FlowGraph
* Materialization of transform, still with old way of terminal operators,
  input/output factories will come next
* New ActorBasedFlowMaterializer in impl2
Merge pull request #15765 from akka/wip-15744-newdsl-transform-patriknw

=str #15744 Hook-up transform to the AST nodes
!str #15121 MaterializerSettings now uses a config object

Resolves #15121
=tes #15777 simple, but stable fix to , or . sensitivity in spec

Solves #15777

Conflicts:
	akka-testkit/src/test/scala/akka/testkit/metrics/reporter/PrettyDurationSpec.scala
Merge pull request #15759 from ktoso/wip-reduce-weight-flow-materializer-ktoso

!str #15121 MaterializerSettings now uses a config object
Merge pull request #15789 from ktoso/port-prettydurationspec-ktoso

=tes #15777 simple, but stable fix to , or . sensitivity in spec (for Validation)
=str #15755 #15756 First stab at input/output factories

* New naming based on Source and Sink
=str #15755 #15756 correct variance annotations

- make HasNoX into pure marker traits
- make materialization type-safe
- remove casting when using EmptyPublisher
=str #15755 mandate materializer for IterableSource

* Source attach to top flow subscriber
=str #15755 implement Sources

* Implement IteratorSource
* and add tests for IterableSource and IteratorSource
* Implement ThunkSource
* Implement FutureSource
* Implement TickSource
=str #15756 Implement Sinks

* Implement FutureSink
* also, make PublisherSink an object
* Implement OnCompleteSink
* Implement ForeachSink
* Implement SubscriberSink
=str #15755 #15756 Some cleanup