#3720 @swamp/cve/dirtyfrag: scan logs are never saved (file writer handle dropped, data name collides with the status resource)

Found while building @swamp/cve/emudhra (#3709), which copies dirtyfrag's structure.

dirtyfrag's methods call context.createFileWriter('log', label) with the same instance name as the status resource they write (label or host), and never return the handle from finalize(). After a scan, swamp data list shows only the status resource; the log file is not recorded.

Two problems:

1. finalize() returns a data handle that has to be included in the method's dataHandles, or the file is not registered.
2. Data names are per model, not per spec, so a file and a resource with the same instance name overwrite each other's versions.

Fix as done in cve/emudhra: name file instances distinctly (for example host-log) and return the finalize() handles alongside the resource handles. Affects scan, scanFleet and mitigate.