Rework hkjn.me/prober interface
Rework hkjn.me/prober interface

Now there's an explicit Result type, that probe users can return from
their Probe() implementations (via the
FailedWith/FailedWithInfo/Passed/PassedWith helper functions, if
desired).

This allows more explicit information to be passed back, and by baking
in the Result value in the Records as well users are free to show the
information, i.e. an URLs leading to more info about the probe
outcome.

hkjn/prober