SpringBoot Provide MvcRequestMatcher.Builder that correctly configures the servlet path

When only one DispatcherServlet servlet mapping, publish MvcRequestMatcher.Builder bean

Closes #37917

Comment From: wilkinsona

Unfortunately, I don't think we can accept a contribution for this one as dealing with DispatcherServlet is rather complicated and we need to be certain that we get it right when it relates to security. For example, one thing that we need to do is to use the DispatcherServletPath. I think we'll also need to spend some time thinking about how we can be certain that there's only a single DispatcherServlet and if there's any chance that one could be "hiding" behind a ServletRegistrationBean. Thanks anyway for the PR but I think it's better if the core team handle this one in collaboration with the Spring Security team. Sorry for the wasted effort here, I've added pending-design-work to #37917 to more accurately reflect its current status.