Resolve memory leaks in RootViewCoordinator

Problem:
- RootViewCoordinator is a singleton
- RootViewCoordinator holds a strong reference to RootViewPresenter
- WPTabBarController implements RootViewPresenter and is presenter as rootViewController
- When WPTabBarController is dismissed, RootViewCoordinator continues to hold a strong reference to a WPTabBarController creating a memory leak

Solution:
- Move presentation logic from WindowsManager to RootViewCoordinator
- Only initialize RootViewPresenter when needed
- Release RootViewPresenter after logging out. Not making RootViewPresenter weak or unowned to avoid further cascading changes through the codebase to handle RootViewPresenter being optional
- RootViewPresenter should not be accessed before the root view is presented. If it happens - print a warning. All the issues should be addressed with further improvements.

WordPress/Classes/System/RootViewCoordinator.swift

@@ -1,4 +1,5 @@
 import Foundation
+import WordPressAuthenticator
 
 extension NSNotification.Name {
     static let WPAppUITypeChanged = NSNotification.Name(rawValue: "WPAppUITypeChanged")
@@ -19,7 +20,17 @@ class RootViewCoordinator {
     static let shared = RootViewCoordinator(featureFlagStore: RemoteFeatureFlagStore(),
                                             windowManager: WordPressAppDelegate.shared?.windowManager)
     static var sharedPresenter: RootViewPresenter {
-        shared.rootViewPresenter
+        guard let rootViewPresenter = shared.rootViewPresenter else {
+            /// Accessing RootViewPresenter before root view is presented is incorrect behavior
+            /// It shows either inconsistent order of app dependency initialization
+            /// or that RootViewPresenter contains actions unrelated to presented views
+            DDLogWarn("RootViewPresenter is accessed before root view is presented")
+            let rootViewPresenter = shared.createPresenter(shared.currentAppUIType)
+            shared.rootViewPresenter = rootViewPresenter
+            return rootViewPresenter
+        }
+
+        return rootViewPresenter
     }
 
     // MARK: Public Variables
@@ -34,7 +45,7 @@ class RootViewCoordinator {
 
     // MARK: Private instance variables
 
-    private(set) var rootViewPresenter: RootViewPresenter
+    private var rootViewPresenter: RootViewPresenter?
     private var currentAppUIType: AppUIType {
         didSet {
             updateJetpackFeaturesRemovalCoordinatorState()
@@ -50,17 +61,39 @@ class RootViewCoordinator {
         self.featureFlagStore = featureFlagStore
         self.windowManager = windowManager
         self.currentAppUIType = Self.appUIType(featureFlagStore: featureFlagStore)
-        switch self.currentAppUIType {
+        updateJetpackFeaturesRemovalCoordinatorState()
+    }
+
+    // MARK: - Root Coordination
+
+    func showAppUI(animated: Bool = true, completion: (() -> Void)? = nil) {
+        let rootViewPresenter = createPresenter(currentAppUIType)
+        windowManager?.show(rootViewPresenter.rootViewController, animated: animated, completion: completion)
+        self.rootViewPresenter = rootViewPresenter
+
+        updatePromptsIfNeeded()
+    }
+
+    func showSignInUI(completion: (() -> Void)? = nil) {
+        guard let loginViewController = WordPressAuthenticator.loginUI() else {
+            fatalError("No login UI to show to the user.  There's no way to gracefully handle this error.")
+        }
+
+        windowManager?.show(loginViewController, completion: completion)
+        WordPressAuthenticator.track(.openedLogin)
+        self.rootViewPresenter = nil
+    }
+
+    private func createPresenter(_ appType: AppUIType) -> RootViewPresenter {
+        switch appType {
         case .normal:
-            self.rootViewPresenter = WPTabBarController(staticScreens: false)
+            return WPTabBarController(staticScreens: false)
         case .simplified:
             let meScenePresenter = MeScenePresenter()
-            self.rootViewPresenter = MySitesCoordinator(meScenePresenter: meScenePresenter, onBecomeActiveTab: {})
+            return MySitesCoordinator(meScenePresenter: meScenePresenter, onBecomeActiveTab: {})
         case .staticScreens:
-            self.rootViewPresenter = StaticScreensTabBarWrapper()
+            return StaticScreensTabBarWrapper()
         }
-        updateJetpackFeaturesRemovalCoordinatorState()
-        updatePromptsIfNeeded()
     }
 
     // MARK: JP Features State
@@ -122,15 +155,6 @@ class RootViewCoordinator {
     }
 
     private func reloadUI(using windowManager: WindowManager) {
-        switch currentAppUIType {
-        case .normal:
-            self.rootViewPresenter = WPTabBarController(staticScreens: false)
-        case .simplified:
-            let meScenePresenter = MeScenePresenter()
-            self.rootViewPresenter = MySitesCoordinator(meScenePresenter: meScenePresenter, onBecomeActiveTab: {})
-        case .staticScreens:
-            self.rootViewPresenter = StaticScreensTabBarWrapper()
-        }
         windowManager.showUI(animated: false)
     }
 

WordPress/Classes/System/WindowManager.swift

@@ -67,7 +67,7 @@ class WindowManager: NSObject {
     ///
     @objc func showAppUI(for blog: Blog? = nil, animated: Bool = true, completion: Completion? = nil) {
         isShowingFullscreenSignIn = false
-        show(RootViewCoordinator.sharedPresenter.rootViewController, animated: animated, completion: completion)
+        RootViewCoordinator.shared.showAppUI(animated: animated, completion: completion)
 
         guard let blog = blog else {
             return
@@ -81,12 +81,7 @@ class WindowManager: NSObject {
     func showSignInUI(completion: Completion? = nil) {
         isShowingFullscreenSignIn = true
 
-        guard let loginViewController = WordPressAuthenticator.loginUI() else {
-            fatalError("No login UI to show to the user.  There's no way to gracefully handle this error.")
-        }
-
-        show(loginViewController, completion: completion)
-        WordPressAuthenticator.track(.openedLogin)
+        RootViewCoordinator.shared.showSignInUI(completion: completion)
     }
 
     /// Shows the specified VC as the root VC for the managed window.  Takes care of animating the transition whenever the existing

WordPress/Classes/ViewRelated/Blog/Blogging Prompts/RootViewCoordinator+BloggingPrompt.swift

@@ -8,7 +8,7 @@ extension RootViewCoordinator {
     }
 
     @objc func updatePromptsIfNeeded() {
-        guard let blog = rootViewPresenter.currentOrLastBlog() else {
+        guard let blog = Self.sharedPresenter.currentOrLastBlog() else {
             return
         }
 
@@ -22,7 +22,7 @@ extension RootViewCoordinator {
         guard Feature.enabled(.bloggingPrompts),
               let siteID = userInfo[BloggingPrompt.NotificationKeys.siteID] as? Int,
               let blog = accountSites?.first(where: { $0.dotComID == NSNumber(value: siteID) }),
-              let viewController = rootViewPresenter.currentViewController else {
+              let viewController = Self.sharedPresenter.currentViewController else {
             return
         }