Document `imagePullPolicy` for Istio Sidecars

We have documented most of the BB package values required to override imagePullPolicy in this document. We are missing the values required to set the pull policy on istio sidecars. We should add this to the document so that it can be used in the future when we setup the "global" value for pull policy. Make sure to test that the values work as documented with an override (ex: override to set pull policy = Always).

NOTE: Suspicion is that these values likely need to be set in this section.

AC:

• pull policy values for sidecar (proxy and proxy init) documented