Update metric calculation for "new" and "closed workload"

Currently, the scope of the report is not taken into account when calculating the metrics, leading to multiple counts.

Ex: conversation is moved from inbox A to B. It will increment the new workload by one (for B) and the closed workload by one (for A). If both A and B are in the scope of the report, moving a conversation should leave the metric untouched as it doe not create nor solves workload