* Introduce a `SplitterSpec` which can accept possible
splitter variants: `expression`, `function`, `ref` etc.
This way we are going to have a complex endpoint configuration
only with a single method argument.
* Use `SplitterSpec` in a newly introduced `splitWith()`
* Deprecate those `split()` methods which use `SplitterEndpointSpec`.
This method are complex enough because of their several arguments
* Refactor some common `MessageHandler` options initialization
into the `ConsumerEndpointSpec.doGet()`
* Disable failing now `MethodInvokingMessageProcessorTests.testCollectionArgument()`:
or Jackson problem, or fresh SF
* Groovy DSL will be fixed in the separate PR:
https://stackoverflow.com/questions/76595843/groovy-selects-a-defaultgroovymethods-split-instead-of-mine-one
34f901f7db