fix(ios): force zero width for empty Text component (#55472)

Summary:
This PR fixes a layout regression in iO where empty <Text /> components render with a non-zero width.

The Motivation: In commit(9fe20d4), the logic to add a placeholder "I" to empty strings was moved from ShadowNode to the platform-specific TextLayoutManager.

While the "I" placeholder provides the correct height, the measurement result also includes the width of the "I" character. This causes empty components to take up horizontal space.

## Changelog:

[IOS] [FIXED] - Force zero width for empty Text components in Fabric to prevent ghost layout artifacts.

Pull Request resolved: #55472

Test Plan:
Render a component with an empty string and a background color:

```
<Text style={{ backgroundColor: 'red' }} />
```

Before: A small red vertical sliver (the width of "I") is visible.
After: The component is invisible (0 width)

## Related issue:

#55468

Reviewed By: cipolleschi

Differential Revision: D94011915

Pulled By: NickGerleman

fbshipit-source-id: 8408dc43f06bd67e5938004148a4c9ebd3939864

Author: Hector-Zhuang

packages/react-native/ReactCommon/react/renderer/textlayoutmanager/platform/ios/react/renderer/textlayoutmanager/TextLayoutManager.mm

@@ -37,7 +37,8 @@
 
   switch (attributedStringBox.getMode()) {
     case AttributedStringBox::Mode::Value: {
-      auto attributedString = ensurePlaceholderIfEmpty_DO_NOT_USE(attributedStringBox.getValue());
+      auto originalAtributedString = attributedStringBox.getValue();
+      auto attributedString = ensurePlaceholderIfEmpty_DO_NOT_USE(originalAtributedString);
 
       measurement = textMeasureCache_.get(
           {.attributedString = attributedString,
@@ -54,6 +55,14 @@
                                                             layoutContext:layoutContext
                                                         layoutConstraints:layoutConstraints];
 
+            // TODO(D63303709): We compensate for the placeholder character
+            // being used to represent empty string. iOS TextLayoutManager
+            // should instead measure using `baseTextAttributes` of the
+            // `AttributedString`.
+            if (originalAtributedString.isEmpty()) {
+              measurement.size.width = 0;
+            }
+
             if (telemetry) {
               telemetry->didMeasureText();
             }