op-chain-ops: Go script forking fix for repeated state-dumps

[protolambda]

Description

The forking state needs to maintain the fallback state as the selected state when forkID == 0. Also clarifies state-dump comments.

Tests

Implemented a regression test, to cover the state dumping, and expected state-changes, over repeated state-dumps on the same script host.

[mslipper]

merged manually