Implement ArbitrumDAO DVP-Based Quorum for Proposals

ArbitrumDAO upgrades quorum to delegated voting power (DVP)-based model: Quorum = min {max quorum, max {ɑ*DVP, baseline quorum}}. Constitutional proposals use ɑ=0.5, baseline 150m ARB, max 450m ARB; non-constitutional use ɑ=0.4, baseline 100m ARB, max 300m ARB. Quorum currently at ~62% of DVP, max quorum aligns with 3% and 4.5% of max supply. Trail of Bits audited.