This commit adds Coroutines support for `@Cacheable`.
It also refines SimpleKeyGenerator to ignore Continuation
parameters (Kotlin does not allow to have the same method
signature with both suspending and non-suspending variants)
and refines
org.springframework.aop.framework.CoroutinesUtils.awaitSingleOrNull
in order to wrap plain value to Mono.
Closes gh-31412
466c8d8f23