Sets the default proxy on @resolver, to be used for any URIs that
don't match #GSimpleProxyResolver:ignore-hosts or a proxy set
via g_simple_proxy_resolver_set_uri_proxy().
If @default_proxy starts with "socks://",
#GSimpleProxyResolver will treat it as referring to all three of
the socks5, socks4a, and socks4 proxy types.
Sets the default proxy on @resolver, to be used for any URIs that don't match #GSimpleProxyResolver:ignore-hosts or a proxy set via g_simple_proxy_resolver_set_uri_proxy().
If @default_proxy starts with "socks://", #GSimpleProxyResolver will treat it as referring to all three of the socks5, socks4a, and socks4 proxy types.