Allow changing mappings of auto-configured Servlet filters

[vpavic]

Spring Boot auto-configures several Servlet filters (various Spring MVC related filters, Spring Security, and so on) an maps them to /** (see AbstractFilterRegistrationBean#DEFAULT_URL_MAPPINGS) but to my knowledge doesn't allow to customize the mappings.

In one recent project we wanted to add an additional Servlet to handle some specific requests, but didn't want to have all the auto-configured filters applied to it. This was a challenge because apparently there's no easy way to change the mappings of auto-configured filters.