[AIP 70] Resume stETH Strategy

Discussion here: https://forum.alchemix.fi/public/d/372-aip-70-resume-steth-strategies/5

A vote "FOR" executes the following changes:

1. Increase the stETH deposit cap on mainnet Alchemix to 3,000 ETH with multisig discretion to decrease to 0 again if necessary.
2. Modify the stETH adapter to utilize the ChainLink price oracle to report the price of stETH, capped at a maximum of 1 ETH per stETH.
3. Update the maxloss() parameter to check stETH vs ETH and increase to 10% (1000 bps). 4, Keep rETH deposit caps at 0 (due to lack of rETH oracle).
4. A raise of 2,000 additional stETH is recommended 1 month after the initial cap raise, at the discretion of the multisig, provided stETH price exceeds 0.99 ETH.

A vote "against" does not authorize these changes.