fix: attach keyboard tracking view in advance and only when window has been changed (#1170)

## 📜 Description

Fixed strange animation introduced by
`react-native-keyboard-controller`.

## 💡 Motivation and Context

This regression was introduced in
#1158
Basiucally I discovered 2 issues:

- the tracking view could be attached later to the window so we could
see "unreal" values, where keyboard height would be equal to whole
screen size and `progress` could be 2+
#1166 (comment)
- since we start to attach tracking view to each new window we can
attach it to system alerts etc.
#1169

So the manner that we choose was slightly agressive. The original issue
was caused by fact that tracking view gets detached when modal appears.
But when `Alert`/transparent `Modal` are shown, then we don't need to
re-attach a veiw, because old view is not detached. Additionally I
didin't like the fact that we subscribe to
`didBecomeVisibleNotification` event, which gets triggered every time
before the keyboard appears (potentially it may slow down the app).

So in this PR I decided to re-work the approach. Now instead of "try to
attach to top window root view" we follow approach "re-attach tracking
view only if current tracking view was detached". And this approach
works better because:
- we don't attach listener for each new window (attach it only when
necessary)
- we attach it **before** keyboard starts its movement.

So new solution seems to work better and fix all the issues caused by
its previous implementation.

Also I think it's worth to mention several solutions that didn't work:
- I tried to use KVO on `view.window` property and it didn't give a
desired behavior (listener was never called);
- I tried to avoid using `keyboardLayoutGuide`, but when keyboard
disappear - I again don't receive animation and animate instantly to the
end position 🤷‍♂️
- I tried to attach tracking view to window but in this case it's not
tracking any updates and it's not visible 🤷‍♂️

Closes
#1169

## 📢 Changelog

<!-- High level overview of important changes -->
<!-- For example: fixed status bar manipulation; added new types
declarations; -->
<!-- If your changes don't affect one of platform/language below - then
remove this platform/language -->

### iOS

- added `isAttaching` property (`willMove` can be called when we call
`removeFromSuperview`/`addSubview` inside `attachToTopmostView` and we
need to filter out these operations to avoid potential bugs;
- replace `didBecomeVisibleNotification` mechanism with
`willMove(toWindow`;
- call `attachToTopmostView` pro-actively on first mount to start window
observation.

## 🤔 How Has This Been Tested?

Tested in example app + repro (iPhone 16 Pro - iOS 26.0, iPhone 14 Pro -
iOS 16.4)

## 📸 Screenshots (if appropriate):

|Before|After|Issue|
|------|-----|------|
|<video
src="https://github.com/user-attachments/assets/0b7ab951-5a19-400e-b540-061df2c933a9">|<video
src="https://github.com/user-attachments/assets/8653bee3-78c4-4b18-a6ea-312923779bd7">|https://github.com/kirillzyusko/react-native-keyboard-controller/issues/1166#issuecomment-3419679794|
|<video
src="https://github.com/user-attachments/assets/a48fb605-d7e9-484a-bec1-c87d601cdd85">|<video
src="https://github.com/user-attachments/assets/614b9c78-b8ae-4918-9e06-8f18e1516a8f">|https://github.com/kirillzyusko/react-native-keyboard-controller/issues/1169|

## 📝 Checklist

- [x] CI successfully passed
- [x] I added new mocks and corresponding unit-tests if library API was
changed

Author: kirillzyusko

ios/observers/movement/KeyboardTrackingView.swift

@@ -15,6 +15,7 @@ final class KeyboardTrackingView: UIView {
   private var keyboardView: UIView? { KeyboardViewLocator.shared.resolve() }
   private var keyboardHeight = 0.0
   private weak var currentAttachedView: UIView?
+  private var isAttaching = false
 
   static let invalidPosition: CGFloat = -.greatestFiniteMagnitude
 
@@ -55,19 +56,22 @@ final class KeyboardTrackingView: UIView {
       name: UIResponder.keyboardDidShowNotification,
       object: nil
     )
-    NotificationCenter.default.addObserver(
-      self,
-      selector: #selector(attachToTopmostView),
-      name: UIWindow.didBecomeVisibleNotification,
-      object: nil
-    )
+    attachToTopmostView()
+  }
+
+  override func willMove(toWindow newWindow: UIWindow?) {
+    // When the view is being removed from the window, we need to re-attach it
+    if newWindow == nil, !isAttaching {
+      attachToTopmostView()
+    }
   }
 
   @objc private func attachToTopmostView() {
     guard let topView = UIApplication.topViewController()?.view else { return }
 
     if currentAttachedView === topView { return }
 
+    isAttaching = true
     removeFromSuperview()
 
     topView.addSubview(self)
@@ -87,6 +91,7 @@ final class KeyboardTrackingView: UIView {
         heightAnchor.constraint(equalToConstant: 0),
       ])
     }
+    isAttaching = false
   }
 
   @objc private func keyboardWillAppear(_ notification: Notification) {