Fix cursor is not centered when cursorHeight is set (non-Apple platforms). (#145829)

## Description

This PRs fixes the cursor vertical position when a custom cursor height is set on non-Apple platforms (on Apple platforms the cursor is already centered) .

| Before | After |
|--------|--------|
| ![image](https://github.com/flutter/flutter/assets/840911/2d1b855d-d36c-4941-85be-5044ea0e9bb2) | ![image](https://github.com/flutter/flutter/assets/840911/306510c8-42ca-45c7-8c25-ddfa2e22c7f3) | 

<details><summary>Code sample used for the screenshots (cursorHeight 18, font size 16, line height 2)</summary>

```dart
import 'package:flutter/material.dart';

void main() async {
  runApp(
    const MaterialApp(
      title: 'Flutter Demo',
      home: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const Scaffold(
      body: Center(
        child: TextField(
          cursorHeight: 18,
          style: TextStyle(fontSize: 16, height: 2),
        ),
      ),
    );
  }
}
``` 

</details> 

## Related Issue

Fixes https://github.com/flutter/flutter/issues/143480

## Tests

Adds 2 tests, updates 1.

packages/flutter/lib/src/rendering/editable.dart

@@ -1793,13 +1793,12 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
     final double caretX = clampDouble(caretRect.left, 0, math.max(scrollableWidth - _caretMargin, 0));
     caretRect = Offset(caretX, caretRect.top) & caretRect.size;
 
-    final double caretHeight = cursorHeight;
+    final double fullHeight = _textPainter.getFullHeightForCaret(caretPosition, caretPrototype);
     switch (defaultTargetPlatform) {
       case TargetPlatform.iOS:
       case TargetPlatform.macOS:
-        final double fullHeight = _textPainter.getFullHeightForCaret(caretPosition, caretPrototype);
-        final double heightDiff = fullHeight - caretRect.height;
         // Center the caret vertically along the text.
+        final double heightDiff = fullHeight - caretRect.height;
         caretRect = Rect.fromLTWH(
           caretRect.left,
           caretRect.top + heightDiff / 2,
@@ -1812,10 +1811,13 @@ class RenderEditable extends RenderBox with RelayoutWhenSystemFontsChangeMixin,
       case TargetPlatform.windows:
         // Override the height to take the full height of the glyph at the TextPosition
         // when not on iOS. iOS has special handling that creates a taller caret.
-        // TODO(garyq): See the TODO for _computeCaretPrototype().
+        // TODO(garyq): see https://github.com/flutter/flutter/issues/120836.
+        final double caretHeight = cursorHeight;
+        // Center the caret vertically along the text.
+        final double heightDiff = fullHeight - caretHeight;
         caretRect = Rect.fromLTWH(
           caretRect.left,
-          caretRect.top - _kCaretHeightOffset,
+          caretRect.top - _kCaretHeightOffset + heightDiff / 2,
           caretRect.width,
           caretHeight,
         );

packages/flutter/test/widgets/editable_text_cursor_test.dart

@@ -1236,7 +1236,7 @@ void main() {
       backgroundCursorColor: Colors.grey,
       controller: controller,
       focusNode: focusNode,
-      style: const TextStyle(),
+      style: const TextStyle(fontSize: 17),
       textAlign: TextAlign.center,
       keyboardType: TextInputType.text,
       cursorColor: cursorColor,
@@ -1267,6 +1267,96 @@ void main() {
   skip: isBrowser && !isCanvasKit, // https://github.com/flutter/flutter/issues/56308
   );
 
+  testWidgets(
+    'Caret with a cursorHeight smaller than font size is vertically centered on non-Apple platforms',
+    (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/143480.
+      final TextEditingController controller = TextEditingController.fromValue(
+        const TextEditingValue(selection: TextSelection.collapsed(offset: 0)),
+      );
+      addTearDown(controller.dispose);
+
+      const double cursorHeight = 12.0;
+      const double cursorWidth = 4.0;
+      const double fontSize = 16.0;
+
+      final Widget widget = EditableText(
+        autofocus: true,
+        backgroundCursorColor: Colors.grey,
+        controller: controller,
+        focusNode: focusNode,
+        style: const TextStyle(fontSize: fontSize),
+        keyboardType: TextInputType.text,
+        cursorColor: cursorColor,
+        cursorHeight: cursorHeight,
+        cursorWidth: cursorWidth,
+      );
+      await tester.pumpWidget(MaterialApp(home: widget));
+
+      final EditableTextState editableTextState = tester.firstState(find.byWidget(widget));
+      final RenderEditable renderEditable = editableTextState.renderEditable;
+
+      // The caretRect is vertically centered.
+      const Rect caretRect = Rect.fromLTWH(
+        0.0,
+        (fontSize - cursorHeight) / 2,
+        cursorWidth,
+        cursorHeight,
+      );
+      expect(
+        renderEditable,
+        paints..rect(color: cursorColor, rect: caretRect),
+      );
+    },
+    variant: TargetPlatformVariant.all(excluding: <TargetPlatform>{TargetPlatform.macOS, TargetPlatform.iOS}),
+    skip: isBrowser && !isCanvasKit, // https://github.com/flutter/flutter/issues/56308
+  );
+
+  testWidgets(
+    'Caret with a cursorHeight bigger than font size is vertically centered on non-Apple platforms',
+    (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/143480.
+      final TextEditingController controller = TextEditingController.fromValue(
+        const TextEditingValue(selection: TextSelection.collapsed(offset: 0)),
+      );
+      addTearDown(controller.dispose);
+
+      const double cursorHeight = 24.0;
+      const double cursorWidth = 4.0;
+      const double fontSize = 16.0;
+
+      final Widget widget = EditableText(
+        autofocus: true,
+        backgroundCursorColor: Colors.grey,
+        controller: controller,
+        focusNode: focusNode,
+        style: const TextStyle(fontSize: fontSize),
+        keyboardType: TextInputType.text,
+        cursorColor: cursorColor,
+        cursorHeight: cursorHeight,
+        cursorWidth: cursorWidth,
+      );
+      await tester.pumpWidget(MaterialApp(home: widget));
+
+      final EditableTextState editableTextState = tester.firstState(find.byWidget(widget));
+      final RenderEditable renderEditable = editableTextState.renderEditable;
+
+      // The caretRect is vertically centered.
+      const Rect caretRect = Rect.fromLTWH(
+        0.0,
+        (fontSize - cursorHeight) / 2,
+        cursorWidth,
+        cursorHeight,
+      );
+      expect(
+        renderEditable,
+        paints..rect(color: cursorColor, rect: caretRect),
+      );
+    },
+    variant: TargetPlatformVariant.all(excluding: <TargetPlatform>{TargetPlatform.macOS, TargetPlatform.iOS}),
+    skip: isBrowser && !isCanvasKit, // https://github.com/flutter/flutter/issues/56308
+  );
+
   testWidgets('getLocalRectForCaret reports the real caret Rect', (WidgetTester tester) async {
     EditableText.debugDeterministicCursor = true;
     addTearDown(() { EditableText.debugDeterministicCursor = false; });