R1:4fd473e7eda6

Remove explicit administrative actions from the user activity log

Summary:
Depends on D20669. Ref T13343. Currently, the user activity log includes a number of explicit administrative actions which some administrator (not a normal user or a suspicious remote address) takes. In most/all cases, these changes are present in the user profile transaction log too, and that's //generally// a better place for them (for example, it doesn't get GC'd after a couple months).

Some of these are so old that they have…