online-phase: algebra: Allocate single result for share and MAC

[joeykraut]

Purpose

This PR makes the following changes to the representation of the secret sharing $\mathbb{F}$-module:

• We allocate one result in the graph per module element
• A module element no longer has a public modifier -- this is subsumed by the appropriate update to the MAC on a shared value

This change also allows the offline phase to cleanly allocate shared values into the fabric; without the need for gates to allocate each components (share and mac) separately.

Testing

• Unit tests pass