🐛 Fix PriorityQueue deadlock on shutdown (#3540)

* 🐛 Fix PriorityQueue deadlock on shutdown

handleReadyItems hands a ready item to a waiting consumer with an
unbuffered send on w.get while holding w.lock. If ShutDown shuts the
w.done channel first, the parked GetWithPriority consumer can return
through <-w.done instead of receiving, so the send blocks forever and the
whole queue deadlocks (every later GetWithPriority and handleAddBuffer
blocks on w.lock).

Wrap the send in a select that also watches w.done so it is cancelled on
shutdown. Add a regression test that runs the reporter's add/get loop and
fails if workers stay blocked after ShutDown.

Reference: kubernetes-sigs/controller-runtime issue 3538
Signed-off-by: arpitjain099 <arpitjain099@gmail.com>

* Address modernize lint findings in shutdown deadlock test

Switch the counted for loops to range-over-int, use WaitGroup.Go for
the worker goroutines, and replace ptr.To with the new(x) builtin, as
flagged by the modernize linter. No behavior change to the test.

Signed-off-by: arpitjain099 <arpitjain099@gmail.com>

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Signed-off-by: arpitjain099 <arpitjain099@gmail.com>