Update implemented v2alpha API services for resource name parsing.

[SanjayVas]

world-federation-of-advertisers/cross-media-measurement-api#29 switched the v2alpha API resources to use resource names instead of the non-standard resource key messages. Some v2alpha services (e.g. related to Exchange resources) have already been implemented. These need to be updated in order to pull in the newer version of the API repo.

For now, having handwritten functions for parsing/assembling each resource name should be sufficient. In the future, we may want to investigate code generation based on the resource annotations in the protobuf so that the name patterns can live in one place.

[SanjayVas]

Closed by #111 and #122.