feat(Android): Add focused states on page transitions (software-mansion#1894)

## Description

Currently, on Android TV devices when user is switching between views
the last focused child is lost. This seems like an incorrect behavior -
In software-mansion#1706 people are reporting that on Android TV the last focused
element should be stored.

This PR introduces the change to remember last focused element on
previous screen.
For now I've added a statement that the last element should be stored
only for Android TV, but we should discuss if we also should store those
elements for classic Android - I've noticed that it's possible to focus
an element on a normal screen, but I've achieved it only by switching
between elements with arrows on keyboard (so is it possible to focus an
element just by touching a screen? Maybe TalkBack is also focusing the
elements?).

<details><summary>
Focusing elements on Android
</summary>


https://github.com/software-mansion/react-native-screens/assets/23281839/4f62ae66-f411-4c45-b678-1e47c3fa4ff2

</details>

Fixes software-mansion#1706. 

## Changes

- Added `isTelevision` method that checks if user is currently using
Android TV.
- Added `lastFocusedChild` variable with an implementation for finding
last focused elements.

## Screenshots / GIFs

Here you can add screenshots / GIFs documenting your change.

You can add before / after section if you're changing some behavior.

### Before


https://github.com/software-mansion/react-native-screens/assets/23281839/0e3e0ad4-a202-43c3-b688-6c66f76a43f8

### After


https://github.com/software-mansion/react-native-screens/assets/23281839/998dfa5c-6def-47f2-b129-425a2257319a

## Test code and steps to reproduce

You can test those changes on `Example` application by switching between
examples with arrows on the keyboard.

## Checklist

- [ ] Ensured that CI passes

Author: tboba

android/src/main/java/com/swmansion/rnscreens/ScreenStackFragment.kt

@@ -19,13 +19,16 @@ import androidx.coordinatorlayout.widget.CoordinatorLayout
 import com.facebook.react.uimanager.PixelUtil
 import com.google.android.material.appbar.AppBarLayout
 import com.google.android.material.appbar.AppBarLayout.ScrollingViewBehavior
+import com.swmansion.rnscreens.utils.DeviceUtils
 
 class ScreenStackFragment : ScreenFragment, ScreenStackFragmentWrapper {
     private var mAppBarLayout: AppBarLayout? = null
     private var mToolbar: Toolbar? = null
     private var mShadowHidden = false
     private var mIsTranslucent = false
 
+    private var mLastFocusedChild: View? = null
+
     var searchView: CustomSearchView? = null
     var onSearchViewCreate: ((searchView: CustomSearchView) -> Unit)? = null
 
@@ -89,6 +92,11 @@ class ScreenStackFragment : ScreenFragment, ScreenStackFragmentWrapper {
         }
     }
 
+    override fun onStart() {
+        mLastFocusedChild?.requestFocus()
+        super.onStart()
+    }
+
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
@@ -123,6 +131,13 @@ class ScreenStackFragment : ScreenFragment, ScreenStackFragmentWrapper {
         return view
     }
 
+    override fun onStop() {
+        if (DeviceUtils.isPlatformAndroidTV(context))
+            mLastFocusedChild = findLastFocusedChild()
+
+        super.onStop()
+    }
+
     override fun onPrepareOptionsMenu(menu: Menu) {
         updateToolbarMenu(menu)
         return super.onPrepareOptionsMenu(menu)
@@ -163,6 +178,16 @@ class ScreenStackFragment : ScreenFragment, ScreenStackFragmentWrapper {
         }
     }
 
+    private fun findLastFocusedChild(): View? {
+        var view: View? = screen
+        while (view != null) {
+            if (view.isFocused) return view
+            view = if (view is ViewGroup) view.focusedChild else null
+        }
+
+        return null
+    }
+
     override fun canNavigateBack(): Boolean {
         val container: ScreenContainer? = screen.container
         check(container is ScreenStack) { "ScreenStackFragment added into a non-stack container" }

android/src/main/java/com/swmansion/rnscreens/utils/DeviceUtils.kt

@@ -0,0 +1,12 @@
+package com.swmansion.rnscreens.utils
+
+import android.content.Context
+import android.content.pm.PackageManager
+
+object DeviceUtils {
+
+    fun isPlatformAndroidTV(context: Context?): Boolean {
+        return context?.packageManager?.hasSystemFeature(PackageManager.FEATURE_LEANBACK) == true
+    }
+
+}