Ensure Parent ConfigurationClass loaded on overrides

Previously ConfigurationClassParser could override a nested
@Configuration without consideration of @Bean's defined in parent
classes.

This commit ensures that if the original ConfigurationClass contains
additional bean definitions it is processed again.

Issue: SPR-10546
Clarified that CronTrigger never schedules overlapping executions

Issue: SPR-10556
(cherry picked from commit 5dbbd8f)
Polishing
Properly handle knownSuperclasses in case of an overridden ConfigurationClass

Issue: SPR-10546