XDCR UI warning when changing source or target nozzle count beyond a recommended limit

Currently, our default setting value for XDCR Source Nozzles per Node and XDCR Target Nozzles per Node in an XDCR replication is 2. It is very easy for an administrator to raise this value by an arbitrary amount, intuitively thinking that this will improve performance. In some cases, values have been raised to disproportionately high amounts (we've seen values as high as 64) which cause very high XDCR CPU utilization, network connectivity issues due to the overwhelming amount of traffic, and worse XDCR performance than the default values.

We should display a warning when customers raise these values beyond a certain amount so that they understand the implications of making these changes. Otherwise, it is very easy to make this change, experience horrible performance degradation in the cluster, and then take a very long amount of time and effort to determine that the root cause was this change.

It would be good to come up with an agreed-upon value as being on the upper end of practicality for the majority of cluster sizes and use cases and then use that value as the trigger for displaying a UI warning about raising nozzle values and the performance implications that come with doing so.