Treasury Configuration(s) for Multi-Chain Spends

[joepetrowski]

Right now, we need the Root origin to do things like convert Treasury DOT into USDT/USDC (e.g. for Fellowship salaries). This is due to a few configuration things, like using the scheduler and sending XCM programs.

The following referenda should be possible without using Root:

• Main Treasury *Spender and Treasurer tracks should be able to manage DOT (e.g. place orders on Hydration or AH)
• Collective sub-Treasuries should be able to manage their DOT and other assets using their collective referenda tracks (e.g. convert DOT to USDT for their salaries or sub-treasury)

cc @muharem

[muharem]

Here is how API for a spend call will look like to facilitate such spends paritytech/polkadot-sdk#4715