Suggestion: simplify setup-dns

[balupton]

Two things have happened since setup-dns was written:

1. Cloudflared now has a simpler setup, allowing cloud-based configuration, which is far easier that the current manual way of managing tunnels via complex configuration files and auth flow
2. The setup-util* convention has happened

As such, this proposal contains:

1. Moving out adguard home, cloudflared, and whatever else into setup-util-* commands
2. Stripping cloudflared of the complexity and just supporting cloud based configuration