SIP-424: Unstaked SNX voting for governance elections

SIP-424 updates Spartan Council election voting so that all SNX holders can vote, not only SNX stakers. SIP-423 sUSD conversion entitlements yet to be claimed count as SNX voting power at the 4:1 conversion ratio. SIP-423 retired the 420 staking system and deferred the replacement staking contract. Until that contract is live, staking is not a usable basis for election voting power. This SIP replaces staker-only election voting with holder voting for all subsequent council elections, or until a later SIP restores the staking model.