DoH/TRR disabled by network.dns.disabled makes it unsafe to test DoH

In #33962 (closed), our patches for network.dns.disabled also block TRR/DoH. This means that if people want to test DoH, they have to enable unproxied DNS as well.

This can be dangerous; while DoH/TRR is proxy-safe, it does have codepaths to issue native queries in the background for performance comparison.

We could change the check in nsHostResolver::TrrLookup() to check a different pref.

Or, we could additionally put the other places where network.dns.disabled back to network.dns.socks_remote_dns.