Direct API for nocopy operations on sender-side and receiver-side
Since the receiver side API (https://charm.cs.illinois.edu/redmine/issues/1236) has restrictions which demand the user to name a generated entry method in a specific manner in order to overload the generated method, it will be a worthwhile effort to have an alternative API which is more direct as compared to entry method overloading and gives user the control to perform GET/PUT calls directly.
- Target version set to 6.9.0
We may want to avoid calling this "direct" since there is already something else called CmiDirect. I think in general the recv-side stuff is the completion of the Zero Copy API, but the fact that we will eventually have 2 APIs for the recv-side stuff will make it a bit confusing (I think of this API as the lower-level one, and the RdmaPost one as the higher-level abstraction).