Send validator sync update messages on changing validator set

[ethanfrey]

Currently we only sync the original validator set but do not send new messages when it changes.

To do so, we need more callbacks from the SDK osmosis-labs/mesh-security-sdk#47

Once that is complete, we need to adapt the contracts to it and propagate the proper ibc packets.

[maurolacy]

This also requires storing the historical validator set on the Provider. Because slashing evidence is provided and would have to be checked at a given height.

At least unbonding period historical data need to be stored. This also raises the issue of pruning / deleting of old data, which is not simple to do with the data structures that we have currently implemented (i.e. SnapshotMap).

Alternatively to sending validator set updates and storing the deltas on the Provider, perhaps the historical validator set (or specific validators data) can be queried from the Consumer. If this can be done efficiently, the need for storing the historical Consumer's validator set(s) on the Provider can be obviated.