Add indication that VDR can handle only resolution vs the full interface

[fqutishat]

https://github.com/hyperledger/aries-framework-go/pull/2473#discussion_r561919857

[troyronda]

I think we need to consider having two sets of VDRs loaded into the framework:

• resolvers
• writers / full lifecycle

and make the writer interface a superset of the resolver interface.