Test robustness model against robustness validators

[serathius]

What would you like to be added?

Robustness tests take a real etcd cluster run some traffic against it. They validate the operation history via a model and additional set of validators. Historically we made mistakes and introduced a bugs into the model or the additional validators. Such bugs are hard to debug because first you need to eliminate that this is an etcd bug.

#16142 proposed to also add a "unit" test that would validate model against the validators (without real etcd) that should help us catch bugs earlier.

Why is this needed?

Should help us avoid bugs in the model code.