feat: implement state storage

[utkuozdemir]

On a best-effort basis, store the state on disk on shutdown & restore it from the disk on startup.

Additionally, bump Go version, deps & rekres.

Closes #54.

[utkuozdemir]

@DmitriyMV Can you review the storage I implemented here (context: https://github.com/siderolabs/discovery-service/issues/54#issuecomment-1957095830)

This is a draft with a naive approach. I simply used boltdb + JSON and the snapshots atm are not periodic.

I could not think of any big problems with this approach, but not sure if this is ok or if we would want to do things very differently.

[utkuozdemir]

Superseded by https://github.com/siderolabs/discovery-service/pull/58