Logical resolvers can not deal with `+` schemes

[jurgenvinju]

Describe the bug

The current way of looking up a logical resolver for a scheme does not allow for + schemes; example if the jar+file:/// scheme was implemented with a logical resolver for the scheme jar then it would not be found because the scheme is never split on + anyway in the logicalToPhysical algorithm.

[jurgenvinju]

That's why #1962 will not support mvn+sources:/// and mvn+javadoc:///; could be added easily to the resolver but the infrastructure in URIResolverRegistry does not allow for it.