Move yETH Token Management Role Temporarily to yChad Pending On-Chain Governance

Per the approved yETH YIP, only three roles are approved to mint yETH:

1. The Pool, holding LSD assets and minting yETH at a 1:1 ratio to the ETH equivalent of these assets.
2. The Bootstrapper, used to launch yETH, with minting enabled only for a limited time period.
3. The POL contract, providing protocol-owned liquidity in pools.

This proposal aims to extend minter permissions to additional contracts via on-chain governance. This facilitates pool upgrades without the need to redeploy yETH. Until such governance is in place, yChad.eth multi-sig will hold this capability.

Specification

New minter roles for yETH can be established through an on-chain vote by st-yETH holders. Prior to the launch of on-chain governance, yChad.eth will retain this authority.