Proposals: Proposal to burn tokens from council mint

[mochet]

Currently on mainnet we're having our first discussion about the council mint replenishment level: https://pioneerapp.xyz/#/forum/thread/269

One thing that may be interesting to have is a proposal that can be triggered n times per council period and can burn some max % of the council mint.

The problem this solves is that it requires a lot less friction than the budget replenishment amount proposal which has a constitutionality of 3.

┆Issue is synchronized with this Asana task by Unito

[bedeho]

1. Hard to reply without a proper problem vs. solution distinction here.
2. There is not budget replenishment proposal: https://handbook.joystream.org/system/proposal-system

[bedeho]

Covered here: #3494