Make runloop command queue unbounded (#986)

Runloop can get dead-locked when it is subscribed to a large amount of partitions.

- The Runloop command queue is a bounded queue, with a fixed size of 1024.
- The Runloop stream takes commands from the queue, process them and offer a new `Poll` command into the stream (when applicable).
- The `.offer` can suspend the fiber when the command queue is already full. this, in turn, makes the entire stream freeze. the underlying kafka consumer will eventually (after `max.poll.interval.ms`) be dropped from the group without any notification to the zstream.
- To fix this, we change the command queue from bounded to unbounded which will not suspend the fiber that adds the `Poll` command

zio-kafka/src/main/scala/zio/kafka/consumer/internal/Runloop.scala

@@ -554,9 +554,6 @@ private[consumer] object Runloop {
     ) extends RebalanceEvent
   }
 
-  // Internal parameters, should not be necessary to tune
-  private final val commandQueueSize: Int = 1024
-
   def make(
     hasGroupId: Boolean,
     consumer: ConsumerAccess,
@@ -572,7 +569,7 @@ private[consumer] object Runloop {
   ): URIO[Scope, Runloop] =
     for {
       _                  <- ZIO.addFinalizer(diagnostics.emit(Finalization.RunloopFinalized))
-      commandQueue       <- ZIO.acquireRelease(Queue.bounded[RunloopCommand](commandQueueSize))(_.shutdown)
+      commandQueue       <- ZIO.acquireRelease(Queue.unbounded[RunloopCommand])(_.shutdown)
       lastRebalanceEvent <- Ref.Synchronized.make[Option[Runloop.RebalanceEvent]](None)
       initialState = State.initial
       currentStateRef <- Ref.make(initialState)