fix(bottom-tabs,iOS): regression in JS tab change - wrong signal sent to controller (#19)

## Description


software-mansion/react-native-screens-labs@6576ef2
introduced a regression causing js tab change to not work.

## Changes

This PR restores correct behaviour on focus change.

## Test code and steps to reproduce

`TestBottomTabs`

## Checklist

- [x] Included code example that can be used to test this change
- [ ] Ensured that CI passes

Author: kkafar

ios/bottom-tabs/RNSBottomTabsScreenComponentView.mm

@@ -122,7 +122,7 @@ - (void)updateProps:(const facebook::react::Props::Shared &)props
 
   if (newComponentProps.isFocused != oldComponentProps.isFocused) {
     _isSelectedScreen = newComponentProps.isFocused;
-    tabItemNeedsAppearanceUpdate = true;
+    [_controller tabScreenFocusHasChanged];
   }
 
   if (newComponentProps.badgeValue != oldComponentProps.badgeValue) {

ios/bottom-tabs/RNSTabBarController.mm

@@ -49,10 +49,12 @@ - (void)setNeedsUpdateOfTabBarAppearance:(bool)needsUpdateOfTabBarAppearance
 
 - (void)reactMountingTransactionWillMount
 {
+  NSLog(@"TabBarCtrl mountintTransactionWillMount");
 }
 
 - (void)reactMountingTransactionDidMount
 {
+  NSLog(@"TabBarCtrl mountintTransactionDidMount running updates");
   [self updateReactChildrenControllersIfNeeded];
   [self updateSelectedViewControllerIfNeeded];
   [self updateTabBarAppearanceIfNeeded];
@@ -69,6 +71,7 @@ - (void)updateReactChildrenControllersIfNeeded
 
 - (void)updateReactChildrenControllers
 {
+  NSLog(@"TabBarCtrl updateReactChildrenControllers");
   _needsUpdateOfReactChildrenControllers = false;
 
   if (_tabScreenControllers == nil) {
@@ -88,6 +91,7 @@ - (void)updateSelectedViewControllerIfNeeded
 
 - (void)updateSelectedViewController
 {
+  NSLog(@"TabBarCtrl updateSelectedViewController");
   _needsUpdateOfSelectedTab = false;
 
 #if !defined(NDEBUG)
@@ -122,6 +126,7 @@ - (void)updateTabBarAppearanceIfNeeded
 
 - (void)updateTabBarAppearance
 {
+  NSLog(@"TabBarCtrl updateTabBarAppearance");
   _needsUpdateOfTabBarAppearance = false;
 
   UIView *_Nullable maybeHostView = [self.view superview];