fix(config-cache): use netip.Addr to unify the IPv6

[karol-kokoszka]

Fixes #4181

This PR uses netip.Addr to try to parse the host parameter (that can be both, IP or DNS).
If it is able to parse the IP, it keeps this parsed IP (as string) as a key.
If it's not able to parse the IP, original string is kept as a key.

---

Please make sure that:

• Code is split to commits that address a single change
• Commit messages are informative
• Commit titles have module prefix
• Commit titles have issue nr. suffix