Originally, the `op_metrics` packaged together query_stats.cpp and curop.cpp, so there were many targets that depended on `op_metrics` because of curop. Now that curop.cpp is not included in the target, there seem to be at least a couple targets that still depend on `op_metrics` but don't need to. We should investigate those and remove unused dependencies.

We could also consider renaming the target since `op_metrics` is broader than its current purpose just with query_stats.