Resolve .onion domains when Tor integration is enabled

[ameshkov]

We can pass traffic through Orbot's proxy, but .onion domains are still unusable.

Possible solution: intercept DNS requests, resolve .onion domains to a private IP and pass .onion domain to SOCKS or HTTPS proxy instead of that private IP.

[ameshkov]

Needs to be checked with new CoreLibs that supports sending UDP over SOCKS5

[sfionov]

Feature request is created in CoreLibs repo:
AdguardTeam/CoreLibs#1386

[sfionov]

AdGuard for Android 4.4 provides new "FakeDNS" setting of outbound proxy. It allows to access .onion domains on Android.

[pedroapero]

Note: it looks like CloudFlare is now hosting a DOH onion service: https://blog.cloudflare.com/welcome-hidden-resolver/
Might be suitable for Tor integration also.