httptrace: improve logging of slow/unexpected http requests

Created by: mrnugget

This does two things:

1. Prints more specific log messages if a request is either too slow or has an unexpected status code (or both!)
2. Introduces per-route overwriting of the threshold. Some routes are slower than others and I don't want to bump the general threshold to 5 seconds for every route, but only for this specific one.

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In practice: this removes the majority of these logs