feat: implement graceful shutdown

What does this MR do?

Close connections and listener and wait for the server to shutdown properly.

Closes #539 (closed)
Closes #680 (closed)

Note: wg.Wait() was removed because the metrics server doesn't handle interrupts.

cc @jaime @vshushlin

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