Add missing reflection hints on Kotlin classes

This commit adds the relevant reflection hints required by
`KotlinDetector`; this class is trying to detect both `kotlin.Metadata`
and `kotlin.reflect.full.KClasses`.

Fixes gh- 31269

spring-core/src/main/resources/META-INF/spring/aot.factories

@@ -1,3 +1,4 @@
 org.springframework.aot.hint.RuntimeHintsRegistrar=\
+org.springframework.aot.hint.support.KotlinDetectorRuntimeHints,\
 org.springframework.aot.hint.support.ObjectToObjectConverterRuntimeHints,\
 org.springframework.aot.hint.support.SpringFactoriesLoaderRuntimeHints