Minimize memory and deserialization overhead when sending requested data over the network

[RitaMAllenCA]

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Description: We currently send a lot of data straight from storage to a peer, without any necessary deserialization occurring. This can be optimized (although potentially unsafe-ly) to directly supply these bytes from LMDB pages from storage; at the very least we should ensure that the wrapped data passes through without being copied straight to the networking layer. The extent of the optimization is to be figured out during the implementation of this ticket. This optimization is strictly for 1.6+, which has the necessary Buf-based data structures already in place. Assignee: me Epic: 2.0.0 Sprint: upcoming Points: 8