Add customizable DOT /DOH support

[cbjn]

Designed to protect user privacy by preventing man-in-the-middle attacks and controlling DNS data.

[Chilledheart]

Give a look at c-ares/c-ares#612

[Chilledheart]

And for iOS, you can apply the profile for the whole system. See DigitaleGesellschaft/DNS-Resolver@08386e6

[Chilledheart]

curl has doh builtin https://github.com/curl/curl/blob/cd937651448b0176dcda544eb6720cfe894573fb/lib/doh.h and https://github.com/curl/curl/blob/cd937651448b0176dcda544eb6720cfe894573fb/lib/doh.c. we can start from it.

     --dns-interface <interface> Interface to use for DNS requests
     --dns-ipv4-addr <address> IPv4 address to use for DNS requests
     --dns-ipv6-addr <address> IPv6 address to use for DNS requests
     --dns-servers <addresses> DNS server addrs to use
     --doh-cert-status Verify the status of the DoH server cert via OCSP-staple
     --doh-insecure Allow insecure DoH server connections
     --doh-url <URL> Resolve host names over DoH

[Chilledheart]

Chromium's DOH support page: https://www.chromium.org/developers/dns-over-https/ https://simpledns.plus/kb/195-how-to-enable-dns-over-https-doh-in-chrome.

[Chilledheart]

cloudflare's doh page: https://developers.cloudflare.com/1.1.1.1/encryption/dns-over-https/

cloudflare's dot page: https://developers.cloudflare.com/1.1.1.1/encryption/dns-over-tls/

[Chilledheart]

rfc for doh: https://datatracker.ietf.org/doc/html/rfc8484

[Chilledheart]

rfc for dot: https://datatracker.ietf.org/doc/html/rfc7858

[Chilledheart]

DoH will be added in #832 and available in commandline "--doh_url URL".

[Chilledheart]

iOS Support is added in #833.