Follow up to #2468, this is the final piece of ADR-016, to allow apps to update their version without a restart.

Originally ADR-016 proposed adding a new field to EndBlock for updating versions, but it was realized in #2636 (comment) that it might make more sense to just add it directly to the ConsensusParams.

Note we forgot to update the changelog in ADR-016 when it was updated for this change in #2667