multiapi design for DPG

[iscai-msft]

Need to discuss more about the multiapi design for DPG

we had talked about keeping api_version solely tied to the request builders, but the UX study might have shown us we want the api version partially on the client to help with things like path formatting when the api version is in the path

once this is set, need to add all of the multiapi tests for LLC

additinally, we need to make sure that api version errors allow users to know which api versions are valid #896