message: docs: update circuit breaking docs to reflect conn pool changes
diff: @@ -14,10 +14,14 @@ configure and code each application independently. Envoy supports various types
  HTTP/2 uses a single connection to each host. If this circuit breaker overflows the :ref:`upstream_cx_overflow
  <config_cluster_manager_cluster_stats>` counter for the cluster will increment.
  * **Cluster maximum pending requests**: The maximum number of requests that will be queued while
  - waiting for a ready connection pool connection. In practice this is only applicable to HTTP/1.1
  - clusters since HTTP/2 connection pools never queue requests. HTTP/2 requests are multiplexed
  - immediately. If this circuit breaker overflows the :ref:`upstream_rq_pending_overflow
  - <config_cluster_manager_cluster_stats>` counter for the cluster will increment.
  + waiting for a ready connection pool connection. Since HTTP/2 requests are sent over a single
  + connection, this circuit breaker only comes into play as the initial connection is created,
  + as requests will be multiplexed immediately afterwards. For HTTP/1.1, requests are added to the list
  + of pending requests whenever there aren't enough upstream connections available to immediately dispatch
  + the request, so this circuit breaker will remain in play for the lifetime of the process.
  + If this circuit breaker overflows the
  + :ref:`upstream_rq_pending_overflow <config_cluster_manager_cluster_stats>` counter for the cluster will
  + increment.
  * **Cluster maximum requests**: The maximum number of requests that can be outstanding to all hosts
  in a cluster at any given time. In practice this is applicable to HTTP/2 clusters since HTTP/1.1
  clusters are governed by the maximum connections circuit breaker. If this circuit breaker
  