Add color to CupertinoButton.filled constructor (#161660)

Issue: https://github.com/flutter/flutter/issues/161590

This pull request adds `color` argument for CupertinoButton.filled
constructor

---------

Co-authored-by: Tong Mu <dkwingsmt@users.noreply.github.com>

packages/flutter/lib/src/cupertino/button.dart

@@ -131,15 +131,14 @@ class CupertinoButton extends StatefulWidget {
 
   /// Creates an iOS-style button with a filled background.
   ///
-  /// The background color is derived from the [CupertinoTheme]'s `primaryColor`.
+  /// The background color is derived from the [color] argument.
-  ///
+  /// The foreground color is the [CupertinoTheme]'s `primaryContrastingColor`.
-  /// To specify a custom background color, use the [color] argument of the
-  /// default constructor.
   const CupertinoButton.filled({
     super.key,
     required this.child,
     this.sizeStyle = CupertinoButtonSize.large,
     this.padding,
+    this.color,
     this.disabledColor = CupertinoColors.tertiarySystemFill,
     @Deprecated(
       'Use minimumSize instead. '
@@ -158,7 +157,6 @@ class CupertinoButton extends StatefulWidget {
     required this.onPressed,
   }) : assert(pressedOpacity == null || (pressedOpacity >= 0.0 && pressedOpacity <= 1.0)),
        assert(minimumSize == null || minSize == null),
-       color = null,
        _style = _CupertinoButtonStyle.filled;
 
   /// The widget below this widget in the tree.

packages/flutter/test/cupertino/button_test.dart

@@ -595,6 +595,33 @@ void main() {
                 .decoration
             as BoxDecoration;
     expect(decoration.color, isSameColorAs(CupertinoColors.systemBlue.darkColor));
+
+    await tester.pumpWidget(
+      CupertinoApp(
+        home: CupertinoButton.filled(
+          color: CupertinoColors.systemRed,
+          onPressed: () {},
+          child: Builder(
+            builder: (BuildContext context) {
+              textStyle = DefaultTextStyle.of(context).style;
+              return const Placeholder();
+            },
+          ),
+        ),
+      ),
+    );
+
+    decoration =
+        tester
+                .widget<DecoratedBox>(
+                  find.descendant(
+                    of: find.byType(CupertinoButton),
+                    matching: find.byType(DecoratedBox),
+                  ),
+                )
+                .decoration
+            as BoxDecoration;
+    expect(decoration.color, isSameColorAs(CupertinoColors.systemRed));
   });
 
   testWidgets("All CupertinoButton const maps keys' match the available style sizes", (