Update Loop for LoopKit changes supporting Learn (LoopKit#2034)

* Updates for Learn app

* Moving RC methods to LoopKit

* Update LDM for move of retrospectionInterval to static var.

Author: ps2

Common/Extensions/GlucoseRangeSchedule.swift

@@ -17,12 +17,3 @@ extension GlucoseRangeSchedule {
         return HKQuantity(unit: unit, doubleValue: value(at: date).maxValue)
     }
 }
-
-
-extension ClosedRange where Bound == HKQuantity {
-    func averageValue(for unit: HKUnit) -> Double {
-        let minValue = lowerBound.doubleValue(for: unit)
-        let maxValue = upperBound.doubleValue(for: unit)
-        return (maxValue + minValue) / 2
-    }
-}