This commit introduces the spring-core-coroutines module
in order to avoid referencing Kotlin code from Java one,
which is currently not supported by Eclipse.
During the build, spring-core-coroutines is merged into
spring-core, so this change is expected to have no impact
for end users.
This module contains functions accessible from Java via
the CoroutinesUtils class to adapt Coroutines and Deferred
instances to and from Mono.
See gh-19975
Sebastien Deleuze