This proposal is to add Sicco Naets as the 2nd Moonbeam Foundation Treasury Council Member, replacing Lina K.

See the [forum post](https://forum.moonbeam.network/t/proposals-mr82-mb120-appointment-of-sicco-naets-as-moonbeam-foundation-treasury-council-member/2176) for more details.

Set the collective's membership.

- `new_members`: The new member list. Be nice to the chain and provide it sorted.
- `prime`: The prime member whose vote sets the default.
- `old_count`: The upper bound for the previous number of members in storage. Used for
  weight estimation.

The dispatch of this call must be `SetMembersOrigin`.

NOTE: Does not enforce the expected `MaxMembers` limit on the amount of members, but
      the weight estimations rely on it to estimate dispatchable weight.

# WARNING:

The `pallet-collective` can also be managed by logic outside of the pallet through the
implementation of the trait [`ChangeMembers`].
Any call to `set_members` must be careful that the member set doesn't get out of sync
with other logic managing the member set.

## Complexity:
- `O(MP + N)` where:
  - `M` old-members-count (code- and governance-bounded)
  - `N` new-members-count (code- and governance-bounded)
  - `P` proposals-count (code-bounded)

#120 Appointment of Sicco Naets as Moonbeam Foundation Treasury Council Member