Introduce a dynamic proposal deposit mechanism influenced by the total
number of active proposals, with the option to set the deposit to none.

The potential cost (e.g., balance hold) for proposal submission and
storage is determined by the implementation of the `Consideration`
trait. The footprint is defined as `proposal_count`, representing the
total number of active proposals in the system, excluding the one
currently being proposed. This cost may vary based on the proposal
count. The pallet also offers various types to define a cost strategy
based on the number of proposals.

Two new calls are introduced:
- kill(origin, proposal_hash): the cancellation of a proposal,
accompanied by the burning of the associated cost/consideration ticket.
- release_proposal_cost(origin, proposal_hash): the release of the cost
for a non-active proposal.

Additionally change: 
- benchmarks have been upgraded to benchmarks::v2 for collective pallet;
- `ensure_successful` function added to the `Consideration` under
`runtime-benchmarks` feature.

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Co-authored-by: command-bot <>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: GitHub Action <action@github.com>