SpringBoot Apply initializers and bean registrations before registering classes in ApplicationContextRunner

See https://github.com/spring-projects/spring-boot/issues/30153#issuecomment-1147318019 for background. We'd like to update ApplicationContextRunner so that initialisers and bean registrations are applied before any configuration classes are registered. This will allow any conditions on those classes to be evaluated against any changes that the initializers and registrations have made.