op-supervisor: use system clock everywhere

interop activity still uses "time" in a bunch of places where it should use system clock. We should update all sites!

Start in the op-supervisor interop activity code and search for every use of "time" that should instead use the system clock. Confirm the intended system-clock abstraction before changing sites. Done means all relevant interop activity sites use the system clock and the affected tests pass.

Written by the indexing model from the issue text.