Migrate ACS farms smart contract to disable automatic harvest on stake and unstake

Currently ACS farms have a 10 ACS transaction fee that occurs on every stake/unstake/harvest. We can migrate the smart contract so the 10 ACS transaction fee occurs only on harvest, and stake/unstake do not automatically trigger a harvest. This would make their behaviour the same as with ACSI farms.

Migrating the smart contract will mean that all users currently staked in ACS farms will have to manually unstake, and restake in the new Farm contract. This process will need to be carefully managed, and entails some risk if not done properly.