Allow customization of prefetch setting

[Yunogamer]

Please allow some customization of "prefetch: yes", such as another linked conf setting to tell unbound when to prefetch domains instead of the current "if domain is queried with less than 10% remaining in TTL" i think it is. For me, thats 360 or less remaining, allowing to keep current TTL but increasing that to like when theres 20%, 25% remaining etc would be nice.

Using Unbound 1.11.0 on x86_64 (dd-wrt).

[a-0-dev]

I second this! Unbound is working quite fine so far, but in my environment low latency is significantly more important than network throughput or memory consumption. So having some handle on unbound's caching aggressiveness (be it with a percentage, a timeout, a memory limit, an entry limit or something else)

Anyways, thanks for producing this awesome DNS resolver ;)