Prior to this commit, registering `HandlerInterceptor`s using the
`InterceptorRegistry` would not guarantee their order of execution. In
fact, `HandlerInterceptor`s would always be executed before
`MappedInterceptor`s.
This change makes `MappedInterceptor` implement the `HandlerInterceptor`
interface, in order to register all interceptors in a single ordered
list. The order of execution of interceptors is now guaranteed in the
`HandlerExecutionChain` built by `AbstractHandlerMapping`.
Issue: SPR-12673
c36435c042