luci-app-https-dns-proxy: bugfix: AdGuard servers URLs

AdGuard seems to have drastically changed their DoH servers URLs, so this change updates
the root/usr/share/https-dns-proxy/providers/com.adguard.dns.json file.
Fixes https://github.com/openwrt/luci/issues/7038



Also include minor Makefile changes for better menuconfig presence.

Signed-off-by: Stan Grishin <stangri@melmac.ca>