SpringBoot Web server customizers are applied twice when creating the child management context

They're registered as beans in the child context through ServletWebServerFactoryAutoConfiguration which is registered with the child context by the ManagementContextFactory:

https://github.com/spring-projects/spring-boot/blob/1e73a7cf8b376ea4b5ead9e56df093e5354c4de7/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/servlet/ServletManagementContextAutoConfiguration.java#L49-L53

They're then called by WebServerFactoryCustomizerBeanPostProcessor.

They're called a second time through ServletManagementWebServerFactoryCustomizer. It's configured with a variety of customizer classes:

Beans of these types are then retrieved from the context and called:

https://github.com/spring-projects/spring-boot/blob/1e73a7cf8b376ea4b5ead9e56df093e5354c4de7/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/web/server/ManagementWebServerFactoryCustomizer.java#L77-L88

As far as I can tell, we only need one of these two mechanisms. If we got rid of the second, it would address #44068 at the same time.

There's a similar arrangement on the reactive side with ReactiveWebServerFactoryAutoConfiguration and ReactiveManagementWebServerFactoryCustomizer that results in the same double customization.