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

[balupton]

Dropping openDNS as they seem to have 3 different filtering tiers, security filtering by default, unfiltered for ipv6, and then family shield, however, they do not provide comprehensive details on what each of these support:

  "opendns-unfiltered": {
    "url": "https://support.opendns.com/hc/en-us/articles/227986667-Does-OpenDNS-Support-IPv6",
    "comment": "Recursive IPv6 DNS resolution and security filtering for IPv6 traffic",
    "ipv4_servers": [
      "208.67.222.222",
      "208.67.220.220"
    ],
    "ipv6_servers": [
      "2620:119:35::35",
      "2620:119:53::53"
    ]
  },
  "opendns-unfiltered": {
    "url": "https://support.opendns.com/hc/en-us/articles/227986667-Does-OpenDNS-Support-IPv6",
    "comment": "RFC-compliant DNS service that does not provide any level of filtering",
    "ipv4_servers": [
      "208.67.222.222",
      "208.67.220.220"
    ],
    "ipv6_servers": [
      "2620:0:ccc::2",
      "2620:0:ccd::2"
    ]
  },

until their docs improve, bye bye, they need to learn from quad9: https://www.quad9.net/service/service-addresses-and-features/

[balupton]

Cloudflared is now entirely focused on their tunnel service which is now configured via the cloud, and their dns service is now handled via their cloudflare warp client rather than the cloudflared proxy-dns custom service; as such I will be deprecating the existing handling of cloudflared, removing the proxy-dns service, and leaving it as only a tool for cloudflared tunnel cloud configs.

I will look into their cloudflare-warp client, but from memory it does not support linux arm so perhaps I'll leave it up to someone else.

This all said, the custom services for encrypted dns were written in a time when there was not native encrypted dns support. Now all modern operating systems implement native support for encrypted dns, so setup-dns can be dramatically simplified.

In which I'll probably only keep support for the custom services of dnscrypt and adguard home. With everything else being for others to handle, as code and sanity is best when those maintaining it maintain only extant code.

Personally, I'm tempted to also deprecate dnscrypt as it is antiquated, however it is still
popular and it will live forever it seems.

If anyone objects, let me know within the next couple of days.

[balupton]

Except for testing on Linux and a few trivial things for tidying it up, this is done locally.