proc/proc: Fix OSX hangs in highly parallel programs
proc/proc: Fix OSX hangs in highly parallel programs

`next` would hang in highly parallel programs, causing test flickers and
unexpected behavior. This patch fixes it by examining all stopped
threads whenever Delve gets a notification, instead of just the thread
that caused the stop.

aarzilli/delve,alexbrainman/delve,go-delve/delve,ironcladlou/delve,yigen520/delve,lukehoban/delve,firebitsbr/delve,jeffallen/delve,dlsniper/delve,go-delve/delve,visualfc/delve,ggndnn/delve,ironcladlou/delve,dlsniper/delve,dr2chase/delve,aarzilli/delve,ignatov/delve,w4ngyi/delve,dr2chase/delve,dlsniper/delve,alexbrainman/delve,waterway/delve,visualfc/delve,dr2chase/delve,beni55/delve,ignatov/delve,beni55/delve,go-delve/delve,alexbrainman/delve,ggndnn/delve,jeffallen/delve,derekparker/delve,aarzilli/delve,derekparker/delve,visualfc/delve,ggndnn/delve,go-delve/delve,lukehoban/delve,firebitsbr/delve,aarzilli/delve,ignatov/delve,derekparker/delve,go-delve/delve,w4ngyi/delve,waterway/delve,yigen520/delve