Ensure that multiple small holders can run a federation of validators

[Geod24]

We want to allow multiple holders, owning less than the threshold (currently 40,000 BOA) to run a validator in a trustless / non-custodian manner.

From the point of view of the network, this would be one single UTXO. On the client side, this UTXO would be made a Schnorr multi signature UTXO (potentially benefitting from k-of-N?).

Each of the holder would then run a node, connected to their multi signature nodes, come to an agreement, and propagate their partially-signed envelope to the federation.

One peer could then be responsible for gathering those partly-signed envelopes and forward it to the network.