Better request failure logging

[eritbh]

Requests not succeeding is a leading cause of Toolbox errors ^{[citation needed]}. However, instructing users to get to the worker inspector to look at request logs is a pain. Surfacing more information about failed requests in the log messages would make troubleshooting issues significantly easier and cut down on the amount of manual backtracing we have to do to find which endpoints could be responsible and identify their failure modes.