Removing, for now, all the reconfigurations from the TLA model.

Few reasons:

1. We don't need to implement them in the first cut of the system.
   a. expansion/contraction of quorum are a very niche feature
   b. node-swap is not super-important if we assume Pods that can be rescheduled with the same identity and the existing data on the EBS volume
2. The TLA model becomes much simpler and runs way faster
3. It's easier to experiment with other changes in the protocol (eg: changing the concept of entry_id / offset)
4. There are several changes that we need to do in any case when we'll add the node-swap: eg: how to propagate snapshots when bootstrapping new followers)