Separate monitorHomeProfiles option that defaults to true

This gives us a way to put just the new home-profiles management in
dry-run mode.

This way, home-profiles management can be gently turned on by first
enabling monitorHomeProfiles, running for awhile, and only then enabling
manageHomeProfiles once it has active-usage data to work with.

This also allows a safer path to flipping the manageHomeProfiles default
from false to true.