power from FieldProjectionCartesianMonitor is calculated by field components in spherical coordinates

[tomflexcompute]

power from FieldProjectionCartesianMonitor is calculated by field components in spherical coordinates. It causes the integral of power over the monitor surface not equal to the net flux since a sin(angle) factor is missing in the integral. This is a bit confusing and makes the power data not convenient to use. We can consider changing the power calculation in this case to use the field components in Cartesian coordinates similar to the Poynting vector calculation.