Clean POSModalManager resources when POS is closed

POSModalManager creates memory leaks by holding closures that deeper in the stack hold POSModalManager, creating reference cycles.

We need to manually break them. We already cal reset() when view disappears. However, it's not called when POS is closed.

Not cleaning POSModalManager results in all POS resources, incuding aggregate models and services duplicated.

Author: staskus

WooCommerce/Classes/POS/Presentation/PointOfSaleEntryPointView.swift

@@ -30,6 +30,7 @@ struct PointOfSaleEntryPointView: View {
         }
         .onDisappear {
             onPointOfSaleModeActiveStateChange(false)
+            posModalManager.onDisappear()
         }
     }
 }

WooCommerce/Classes/POS/Presentation/Reusable Views/POSModalManager.swift

@@ -26,6 +26,10 @@ class POSModalManager: ObservableObject {
         allowsInteractiveDismissal = allowed
     }
 
+    func onDisappear() {
+        reset()
+    }
+
     private func reset() {
         onDismiss = nil
         allowsInteractiveDismissal = true