```
If 1000 potential peers are known, wait for 5m before querying DNS seeds
for more peers, since eventually the addresses we already know should
get us connected. Also check every 11s whether we've got enough active
outbounds that DNS seeds aren't worth querying, and exit the dnsseed
thread early if so.
DNS seeds: don't query DNS while network is inactive
```
Backport of core PR16939.