Back to work on Supavisor

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+ Supavisor deployed in many regions, but some still remaining
+ Working on Supabase Updater for Elixir, which is our own deployment system
+ Updated `systemd` library with support for `notify-reload` service type

* More tests
* Migrate `systemd` journal handler from `enough` to `logger_udp`
* Add automatic detection of instance metadata to Supavisor

- Still haven't started dogfooding
- Updater was quickly pieced together and it is not the cleanest codebase
- There is a lot of churn in our issue tracker and it is hard to keep up
- I am currently left mostly alone in Supavisor project which make it hard to
  keep up