EntityManagerBeanDefinitionRegistrarPostProcessor should set primary flag on EntityManager bean definitions

[schosin]

When creating multiple LocalContainerEntityManagerFactoryBean beans and marking one or more as primary, the created EntityManager beans should be marked as primary as well.

This change would make it easier to add another EntityManager to an existing application as no further code changes are necessary. Currently Spring fails to autowire EntityManager as there is no primary bean available.

This should also fix spring-projects/spring-framework#24097.

[mp911de]

See also AnnotationConfigUtils.processCommonDefinitionAnnotations for possible missing flags.