changefeedccl: Remove "ugly hack" from nemesis tests

**Is your feature request related to a problem? Please describe.**
In order to disable behavior for certain sinks in nemesis tests we string match against the name of the test.
```
// TODO(dan): Ugly hack to disable `eventPause` in sinkless feeds.
isSinkless := strings.Contains(testName, "sinkless")
```

**Describe the solution you'd like**
We should put multiple tests in nemeses_test.go, one for each sink, and then manually pass in the sink values to nemesis.

Jira issue: CRDB-46483