Adding read only persisted aggregation to the report generation widget in APIM Analytics 3.2.0

**Description:**
The dashboard node is going OOM when trying to generate the monthly usage reports.
We need to add persistedAggregation read-only property to the report widget.

**Suggested Labels:**
apim-analytics-3.2.0

**Affected Product Version:**
apim-analytics-3.2.0
