[PIP-030] Add Curve and Convex receivers for ULTRA/USDC pool

This proposal aims to add receivers for the ULTRA/USDC pool on both Curve and Convex. It will allow vePRISMA voters to direct PRISMA emissions to the pool once it is passed as a gauge.

Read: https://gov.prismafinance.com/t/pip-030-add-curve-and-convex-receivers-for-ultra-usdc-pool/149