Add a new RecordType<R extends Record> type to make up for the missing recursive type definition on Record

[lukaseder]

As long as Row and Record do not correctly specify their R types (see #2570), there is no appropriate type to contain both a Field<?>[] and the associated R type for a given context.

This can be circumvented in the 3.x release stream, by adding a redundant RecordType<R>, which can then be used in new API such as the one introduced by Configuration.recordMapperProvider() (see #2311).

The new type is redundant with Row, as it will have almost the same purpose.