Introduce proposal type to limit group budget refills per term

## Context
- #4622
- #3355

## Rationale
Currently council is able to empty an unlimited amount per term to any group.
This change introduces a budget regiment which reduces the risk of one council suddenly emptying the whole budget.

## Scope
- The council approves a group budgets limit proposal with `constitutionality=2` covering all groups.
- On execution the limits are saved in the pallet and considered by future `update group budget` proposals.
- Option A: Council still has to manually trigger refills and can decide to mint less than projected before.
- Option B: Group budgets are filled automatically based on the approved projections.
- Group budgets are filled based on set group priorities as soon as the council budget holds sufficient funds.
- If the council budget is depleted remaining amounts are paid daily, after council budget replenisment.