Improve Servlet and Filter registration logging

[bclozel]

This issue is related to #13511 and #14292 - about improving the logging experience in Spring Boot.

In comment on SPR-17450, someone mentioned that the Servlet Filter registration logs are not consistent with what we've done so far:

INFO 14944 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'characterEncodingFilter' to: [/*]
INFO 14944 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'hiddenHttpMethodFilter' to: [/*]
INFO 14944 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'formContentFilter' to: [/*]
INFO 14944 --- [           main] o.s.b.w.servlet.FilterRegistrationBean   : Mapping filter: 'requestContextFilter' to: [/*]
INFO 14944 --- [           main] .s.DelegatingFilterProxyRegistrationBean : Mapping filter: 'springSecurityFilterChain' to: [/*]

@rstoyanchev indeed suggests to reconsider the logging level and could log everything on a single line with a map-like structure:

CharacterEncodingFilter [/*], HiddenHttpMethodFilter [/*], FormContentFilter [/*], ...

Currently we're logging that information:

• at INFO level in AbstractFilterRegistrationBean.configure for embedded and WAR deployments
• at DEBUG level in ServletContextInitializerBeans for embedded deployments only

I think we should remove all the above logging information and replace it with one-liners in ServletContextInitializerBeans at DEBUG level, and add that class to the web logging group.