Keep the Alchemy rebalanced cards as options

Arena just ended Alchemy's rebalanced cards, reverting them all to their original balance. Since Forge has previously applied changes to rebalanced cards, I thought I should official request Forge should keep them
1: HBG, a unique draftable set, was balanced around these (e.g., the dragon orbs being omnimana to splash in some off color dragons)
2: It adds some extra variety in omni-format game modes (e.g., Adventure)
3: They can already be turned off with the other Alchemy cards.

Start by locating how Forge represents Alchemy's rebalanced cards and how the existing Alchemy-card toggle is applied, using the Arena, HBG, and Adventure references as context. Done means the rebalanced cards remain available as options, while the existing control can disable them together with the other Alchemy cards.

Written by the indexing model from the issue text.