Add an option to disable caching of NXDOMAIN responses

### Prerequisites

- [X] I have checked the [Wiki](https://github.com/AdguardTeam/AdGuardHome/wiki) and [Discussions](https://github.com/AdguardTeam/AdGuardHome/discussions) and found no answer

- [X] I have searched other issues and found no duplicates

- [X] I want to request a feature or enhancement and not ask a question

### The problem

I have Adguard configured to forward lookups of internal domain names to the router dns server with this rules:

````
[/internal.public.tld/]192.168.128.1
[/128.168.192.in-addr.arpa/]192.168.128.1
[//]192.168.128.1
[/in-addr.arpa/]192.168.128.1
[/ip6.arpa/]192.168.128.1
````

The router's dnsmasq server is setup to advertise this internal.public.tld to local dhcp clients.
This internal subdomain does not exist in the public dns but public.tld does, I think this is whats called split horizon dns.
When ADGH receives queries for this subdomain it correctly forwards them to the routers ip.
When the routers ip is not available (restarted for example), ADGH forwards this queries to upstream dns servers.
This probably should not happen, but maybe its a misconfiguration from my setup.
This queries en up in a NXDOMAIN response as they should be.
This response is stored in the cache.
When router dns server is available again, the queries for this internal subdomain are still answered from the cache, which in turn results in NXDOMAIN responses, presumably til the TTL for the cache entries expires.

### Proposed solution

Add an option to disable caching of NXDOMAIN responses

### Alternatives considered and additional information

Add a filter to disable any forwarding for a defined internal subdomain