This commit also contains changes to `ServletContextInitializerBeans`.
`ServletContextInitializerBeans` can now be configured to only look
for specific ServletContextInitializer subclasses, defaulting to
ServletContextIntializer.class. `SpringBootMockMvcBuilderCustomizer`
only cares about filters so it was unnecessary to look for all
`ServletContextInitializer`s. Additionally, adapting `Servlet` beans
caused a cycle once the `DispatcherServlet` bean was added and the
customizer only needs to adapt `Filter` beans.

Closes gh-13241