ExpansionTile Unable to remove right padding from title (#145271)

This PR makes it possible to remove the hard-coded 32.0 unit padding coming from ListTile when trailing is not null. Which it always it as `ExpansionTile` always provides a widget there. Currently there is no way to remove it and people have to hack around it: e.g. 
https://stackoverflow.com/questions/54714836/how-to-remove-default-padding-from-expansiontiles-header

The issue is quite old and I came across it today and decided to put together a quick fix.

Fixes #145268

The change should be non-breaking as the default stays the same. But I have no issue with changing something if requested. (naming-wise, functionality-wise etc...)

packages/flutter/lib/src/material/expansion_tile.dart

@@ -235,6 +235,7 @@ class ExpansionTile extends StatefulWidget {
     this.onExpansionChanged,
     this.children = const <Widget>[],
     this.trailing,
+    this.showTrailingIcon = true,
     this.initiallyExpanded = false,
     this.maintainState = false,
     this.tilePadding,
@@ -322,6 +323,9 @@ class ExpansionTile extends StatefulWidget {
   /// may replace the rotating expansion arrow icon.
   final Widget? trailing;
 
+  /// Specifies if the [ExpansionTile] should build a default trailing icon if [trailing] is null.
+  final bool showTrailingIcon;
+
   /// Specifies if the list tile is initially expanded (true) or collapsed (false, the default).
   final bool initiallyExpanded;
 
@@ -731,7 +735,7 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
                 leading: widget.leading ?? _buildLeadingIcon(context),
                 title: widget.title,
                 subtitle: widget.subtitle,
-                trailing: widget.trailing ?? _buildTrailingIcon(context),
+                trailing: widget.showTrailingIcon ? widget.trailing ?? _buildTrailingIcon(context) : null,
                 minTileHeight: widget.minTileHeight,
               ),
             ),

packages/flutter/test/material/expansion_tile_test.dart

@@ -1532,4 +1532,40 @@ void main() {
     expect(find.text('Child 0'), findsOneWidget);
     expect(controller.isExpanded, isTrue);
   });
+
+  testWidgets('ExpansionTile does not include the default trailing icon when showTrailingIcon: false (#145268)', (WidgetTester tester) async {
+    await tester.pumpWidget(const MaterialApp(
+      home: Material(
+        child: ExpansionTile(
+          enabled: false,
+          tilePadding: EdgeInsets.zero,
+          title: ColoredBox(color: Colors.red, child: Text('Title')),
+          showTrailingIcon: false,
+        ),
+      ),
+    ));
+
+    final Size materialAppSize = tester.getSize(find.byType(MaterialApp));
+    final Size titleSize = tester.getSize(find.byType(ColoredBox));
+
+    expect(titleSize.width, materialAppSize.width);
+  });
+
+  testWidgets('ExpansionTile with smaller trailing widget allocates at least 32.0 units of space (preserves original behavior) (#145268)', (WidgetTester tester) async {
+    await tester.pumpWidget(const MaterialApp(
+      home: Material(
+        child: ExpansionTile(
+          enabled: false,
+          tilePadding: EdgeInsets.zero,
+          title: ColoredBox(color: Colors.red, child: Text('Title')),
+          trailing: SizedBox.shrink(),
+        ),
+      ),
+    ));
+
+    final Size materialAppSize = tester.getSize(find.byType(MaterialApp));
+    final Size titleSize = tester.getSize(find.byType(ColoredBox));
+
+    expect(titleSize.width, materialAppSize.width - 32.0);
+  });
 }