refactor: stop passing file descriptors around and use net.Listen directly

What does this MR do?

Using file descriptors directly is really fragile and prone to error, some of those shortcomings were outlined in #114 (closed). Since we moved away from the daemon-like architecture (see #133 (closed)) we don't need to pass fd around anymore.

TODO

• I added the Changelog trailer (e.g. Changelog: added) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines