Spring Perform explicit class checks in ReactiveAdapterRegistry [SPR-17000]

Sébastien Deleuze opened SPR-17000 and commented

In order to allow Spring Framework applications running as GraalVM native images, we should perform explicit class checks instead of catching Throwable in order to avoid UnsupportedFeatureError: Unresolved element found errors.

Issue Links: - #21529 Initial GraalVM native images (Substrate VM) support ("is depended on by")

Referenced from: commits https://github.com/spring-projects/spring-framework/commit/9b7a492bc95c8c1f3e3abfe055defa3722a0aa45, https://github.com/spring-projects/spring-framework/commit/dcbaecea2a73c10580e184b927c3747a6c6fd900