request: AdGuard dns exclusive param to choose their server location

Since this is developed by Adguardteam, and has things exclusive to Adguard DNS like dns-over-QUIC support, a param to choose adguard dns server would be most welcomed since there isn't currently a way to resolve misrouting seen anywhere except "adding more servers" and many users are having a problem of 300ms+ ping time: https://github.com/AdguardTeam/AdGuardDNS/issues/99

example:
`dnsproxy -adguardserver Stockholm`

since direct IPs of regional adguard servers don't currently accept queries from the outside and there's a need to choose filtering method (family \ general), it'd require some adjustment to server software but it's not impossible for AdGuard team I believe