Add full regex support for $network rules

[sxgunchenko]

For now, only wildcards are supported (like 127.0.*$network), but there is a feature request for full regex support (see AdguardTeam/AdguardForAndroid#3694).
The syntax of $network rules with regex mask should be the same as for other basic rules (like /.+:[1-3][0-9]{2,5}/$network).

[sfionov]

Such rules can't be converted to CIDR kernel rules (feature used on Mac). But anyway they will be applied on proxy level.

[ameshkov]

feature used on Mac

On pre-BigSur Mac you mean? :)