Deactivates apps by backing up + deleting them on iOS 13.5+

Deactivating apps by removing their profiles no longer works on iOS 13.5. Instead, AltStore will now back up the app by temporarily replacing it with AltBackup, then remove the app from the phone.

AltStore/Operations/RefreshGroup.swift

@@ -21,6 +21,10 @@ class RefreshGroup: NSObject
         
     private(set) var results = [String: Result<InstalledApp, Error>]()
     
+    // Keep strong references to managed object contexts
+    // so they don't die out from under us.
+    private(set) var _contexts = Set<NSManagedObjectContext>()
+    
     private var isFinished = false
     
     private let dispatchGroup = DispatchGroup()
@@ -33,6 +37,8 @@ class RefreshGroup: NSObject
         super.init()
     }
     
+    /// Used to keep track of which operations belong to this group.
+    /// This does _not_ add them to any operation queue.
     func add(_ operations: [Foundation.Operation])
     {
         for operation in operations
@@ -57,6 +63,14 @@ class RefreshGroup: NSObject
     func set(_ result: Result<InstalledApp, Error>, forAppWithBundleIdentifier bundleIdentifier: String)
     {
         self.results[bundleIdentifier] = result
+        
+        switch result
+        {
+        case .failure: break
+        case .success(let installedApp):
+            guard let context = installedApp.managedObjectContext else { break }
+            self._contexts.insert(context)
+        }
     }
     
     func cancel()