Unleash / unleash / 21901655711

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fix MaxListenersExceededWarning in tests (#11316)

## `yarn test` will print a buch of warnings: 

### 11 listeners
```
(node:16735) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 request_time listeners added to [EventEmitter]. MaxListeners is 10. Use emitter.setMaxListeners() to increase limit
(Use `node --trace-warnings ...` to show where the warning was created)
```

### 200 listeners
and a second one where after experimenting the number is around 200

```
// MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 200 UPDATE_REVISION listeners added to [ConfigurationRevisionService]. MaxListeners is 199. Use emitter.setMaxListeners() to increase limit
(Use `node --trace-warnings ...` to show where the warning was created)
```

###  Testing 

```
yarn test | grep MaxListenersExceededWarning
```

## About the changes

* clean listeners in test to fix the 11 listeners warning
* The other one is caused by `configurationRevisionService` that's a
singleton in tests. Increasing the number of connections in
`createFakeFrontendApiService` seems like a least intrusive option.
* Some small tweaks to `yarn ci` that probably only I use so please
ignore.

Closes #

### Important files


## Discussion points

* It might be a good idea to increase limit from 200 to some higher
number like 300 so the warning won't show up next time we add a test...
* But, the other option is to take a little more time to think if we can
somehow get rid of the singleton in tests to prevent this from
happening.

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