Cache#get can hang in case of interruption

[ghostdogpr]

Had a production incident because Cache#get was hanging forever. Finally found the culprit: when get is interrupted, there is a possibility for it to be interrupted before onInterrupt is set but after the map is updated with the Pending state. In that case it stays Pending until the cache is invalidated.

Reproducer:

    test("ensure get is not hanging when we interrupt right after a get in another fiber") {
      for {
        cache <- Cache.make(10, Duration.Infinity, Lookup((_: Unit) => ZIO.succeed(1)))
        task1  = (cache.invalidate(()) *> cache.get(())).fork.flatMap(_.interrupt)
        _     <- ZIO.forkAll(List.fill(1000)(task1))
        _     <- cache.get(()).exit.timeoutFail("hanging")(3.seconds).forever.timeout(7.seconds)
      } yield assertCompletes
    } @@ TestAspect.withLiveClock