Additional logging for `jetpack_deleted_user` and `jetpack_removed_user_from_blog`.

Jetpack currently records two kinds of user manipulation activity (among others): `jetpack_deleted_user` and `jetpack_removed_user_from_blog`. From what I can see, however, events for these actions don't necessarily include 1) who is modifying a given user, and 2) who the user being modified is. It would be great if additional logging were made available so that the modifying user, and the user being modified, were both surfaced in logs (e.g. in Kibana).

See internal reference for full context: 6660-gh-Automattic/jpop-issues