Added instrumentation for Paginator and RetryPolicy.

Added instrumentation for Paginator and RetryPolicy so API clients can understand the number of requests executed per search including the number of retry requests.
"Less is more" has usually been my policy, and eventually keeping things to their most necessary is a good thing - though too many levels of indirection become burdensome.  

But at this time we're still troubleshooting many things, so keeping it public for troubleshooting purposes can save a lot of headaches.