[FIP-451] Add Royco SLP to sfrxUSD Strategies

Summary

Authors Frax Core Team --- ## Summary This proposal seeks to authorize the sfrxUSD strategy framework to allocate up to 1,000,000 frxUSD into the Royco SLP. The objective is to provide redemption liquidity for sr-srRoyUSDC while earning yield generated by the underlying srRoyUSDC strategy, expanding sfrxUSD's portfolio of governance-approved yield strategies and strengthening frxUSD's role within the Royco ecosystem. --- ## Background & Motivation As sfrxUSD continues to...