[robustness tests] Add Watch without PrevKV or ProgressNotify to Kubernetes traffic generator

### What would you like to be added?

Kubernetes traffic generator should use `Watch` without `ProgressNotify` (like `apiserver` does for `events`) and without `PrevKV` (like it does for `compact_rev_key`). The latter will also help cover the case of non-recursive watch.

In case of `Watch`es on `events` resource, traffic generator could also open multiple watch streams within the same gRPC stream to better mimic what `apiserver` does.

Work on this was partially started in https://github.com/etcd-io/etcd/pull/20577

### Why is this needed?

Part of https://github.com/etcd-io/etcd/issues/15820 and https://github.com/etcd-io/etcd/issues/20182