[Antithesis] Test with dynamic cluster configuration

### What would you like to be added?

Currently, the etcd cluster composition configuration for Antithesis tests is fixed. That is, the docker-compose file has a fix instance of the etcd cluster member, which we currently configure as a single or three member cluster.

We want to explore if it is possible to run tests in Antithesis where we can simulate the cluster can dynamically scale out or in.

### Why is this needed?

Exploration with more advanced test configurations.

The issue names the docker-compose file used for Antithesis tests; start by reviewing how the fixed one- or three-member etcd cluster is configured. Investigate whether Antithesis can change cluster membership during a test and how scale-out and scale-in would be represented. Done means a working test configuration that exercises dynamic cluster scaling.

Written by the indexing model from the issue text.