Supply-Curve-Aggreation: Take partial exclusions into account for data_layer characterization sums

[WilliamsTravis]

Bug Description In supply-curve-aggregation, the "sum" characterization method for data_layers appears to be adding the pixel counts within a supply curve point before removing partial exclusions. We would like this figure to allow us to calculate the area of non-excluded land within each characterization.

Expected behavior The sum of a characterization layer is a float taking into account partial exclusions.

System (please complete the following information):

• OS: Linux
• Compute hardware Eagle
• Version: v0.4.43

[MRossol]

@WilliamsTravis is this what you were envisioning: https://github.com/NREL/reV/blob/77c77a065b6be7704eae09c13e1e964ddaa289e5/reV/supply_curve/point_summary.py#L472-L473