we generally do not want to catch or throw these. catching them to print
and discard is fine, tests are largely exempt, and cases in which we can
be certain where the exception came from are also fine to *catch*. we'll
try to never *throw* (or rethrow) these if possible though because doing
so will make it impossible to construct async traces for the exceptions.
Change-Id: I3b71c32ecd16afc2246c946472f5629a1fa31f2c
like kj::joinPromisesFailFast this allows waiting for the results of
multiple promises at once, but unlike it not all input promises must
be complete (or any of them failed) for results to become available.
Change-Id: I0e4a37e7bd90651d56b33d0bc5afbadc56cde70c
eldritch horrors