Convert Part of DOT Assets to Stablecoins

This is a new referendum to gradually convert part of the Polkadot Treasury's DOT assets into stable coins (specifically USDT and USDC). Similar to referendum 457, it uses Hydration's DCA feature to sell a fixed amount of DOT per day. The allotted amount covers one year of conversions.

Unlike 457, rather than acquiring a fixed amount of USDT/C per trade, this sells a fixed amount of DOT per trade.

See the proposal doc for more details, methodology, and calculations.