Polish ResolvableType & SerializableTypeWrapper

Fix 'missing serialVersionUID' warnings, support for void.class types
and refine resolve() algorithm to support narrowed types.

Issue: SPR-10973
Support for MultiValueMap in MapToMapConverter

Refactor TypeDescriptor to use ResolvableType in order to retain full
generic type information, in the process fixing MultiValueMap support
in MapToMapConverter.

Issue: SPR-9499