Add built-in support for n98-Magerun2 in the deploy container

**Is your feature request related to a problem? Please describe.**
Magerun2 solves some annoyances devs have to deal with when developing with Magento. Directly running cronjobs for example.

**Describe the solution you'd like**
Would be great if the `deploy` container (so the [`cli`](https://github.com/magento/magento-cloud-docker/tree/develop/images/php) php images) now used for magento commands would also support [running `n98-magerun2`](https://github.com/netz98/n98-magerun2/). For example:

```
docker-compose run --rm deploy magerun2
```

Note that `magerun2` will also expose the regular Magento CLI, so it could also be used as a replacement of the `magento-command` command.

**Describe alternatives you've considered**
Fixing the container myself locally. But that means my colleagues would have to go through the same steps as well. Changing it at the source would be a better solution IMO.

**Additional context**
Magerun2 is under the [MIT licence](https://github.com/netz98/n98-magerun2/blob/develop/MIT-LICENSE.txt), so license wise I think it should be fine to distribute the Magerun binary directly in the container.

The original https://github.com/meanbee/docker-magento2 already [had](https://github.com/meanbee/docker-magento2/blob/master/7.4-cli/Dockerfile#L80-L81) this [exact functionality](https://github.com/meanbee/docker-magento2/blob/master/7.4-cli/bin/magerun2). Perhaps most (all?) of what is needed can be taken from that repository.