Configurable (via Governance Call) Funds Distribution

[joepetrowski]

Right now, the two types that govern funds going into the Treasury from inflation are EraPayout and RewardRemainder.

EraPayout returns how much of the payout should not go to validators, and RewardRemainder handles that amount. Of course it would be possible to change this implementation in a runtime upgrade to split it into several accounts, but ideally it would be configurable on its own. I would imagine the solution being a small pallet that maintains an AccountId => PerBill table and a dispatchable function to update the table.

This is especially relevant with the introduction of new sub-treasuries, e.g. for the Technical Fellowship. We might introduce a new collective and want to update how remainder funds are distributed. For example, we could have:

Account	Amount
Tech Fellowship	5%
Collective B	5%
Collective C	7%
Main Treasury	83%

If a new collective (D) wants to transition from one-off Treasury proposals to a steady influx of funds, a proposal could call (e.g.) set_distribution_table(new):

Account	Amount
Tech Fellowship	5%
Collective B	5%
Collective C	7%
Collective D	2%
Main Treasury	81%

[kianenigma]

Can be solved as a part of polkadot-fellows/RFCs#89