SAIP #61: Add single-sided gmBTC and single-sided gmETH Cauldrons

TL;DR: Introduce two new markets on Arbitrum using single-sided gmBTC and single-sided gmETH as collateral.

Cauldron Parameters: gmBTC: Loan-to-Value (LTV): 85% Interest Rate: 8% Borrow Fee: 0.3% Liquidation Fee: 6% gmETH: Loan-to-Value (LTV): 85% Interest Rate: 8% Borrow Fee: 0.3% Liquidation Fee: 6% Initial Top-Up: Cumulative 4 million MIM across both cauldrons, starting with low six-figure amounts for beta testing, and ability to scale up to 10m.