Prior to this commit, the Spring Framework build would mix proper
framework modules (spring-* modules published to maven central) and
internal modules such as:
* "spring-framework-bom" (which publishes the Framework BOM with all
modules)
* "spring-core-coroutines" which is an internal modules for Kotlin
compilation only

This commit renames these modules so that they don't start with
"spring-*"; we're also moving the "kotlin-coroutines" module under
"spring-core", since it's merged in the resulting JAR.

See gh-23282