Gather

The gather operator is a special memory operator: it reads ts1 and ts2 sources, computes addresses based on ts1 addresses and ts2 values, and then performs additional reads using those computed addresses. We need to account for this behaviour.

In the zkVM, we first check that the gather-read values are correct, then verify that the addresses are computed correctly from the ts1 addresses and ts2 values, and finally confirm that the gather reads match TdWrites.