This commit introduces the following changes:
 - The new CorsConfigurationMapping class allows to share the mapped
   CorsConfiguration logic between AbstractHandlerMapping and CorsFilter
 - In AbstractHandlerMapping, the Map<String, CorsConfiguration>
   corsConfiguration property has been renamed to corsConfigurations
 - CorsFilter allows to process CORS requests at filter level, using any
   CorsConfigurationSource implementation (for example
   CorsConfigurationMapping)

Issue: SPR-13192