The documentation for `ConnectionPoolStats.totalCreated` suggests that the metric can only monotonically increase, but this is not the case. When appending stats, the `ConnectionPool` iterates through the stats for each host and adds them to the `ConnectionPoolStats` fields. However, hosts that are idle will eventually timeout and shutdown meaning we delete the totalCreated stats along with it. This can cause unexpected drops to the totalCreated metric.

We should keep a separate counter for created connections that have expired and add them to the ConnectionPoolStats after appending all the host stats.