perf(gas): optimize stage per wallet limits gas

[jessefriedland]

• saves every minter 20k of gas (@ 50 gwei this is ~$2, @ 100 gwei this is ~$4)
• pack into aux on the erc721a ownership storage
• ⚠️ caveat ⚠️: limits # of stages to 4 (or 8 if max limit per wallet of 255 is acceptable)

gas averages before optimization

gas averages post optimization