CW-376-picker-ui-issue (#919)

* feat: use common modal widget for repeated picker logic and display

* refactor: rename widget

* refactor: clear wrapper logic from picker widget and move title to hasTitle

* Minor code readability enhancements [skip ci]

---------

Co-authored-by: OmarHatem <omarh.ismail1@gmail.com>

lib/src/widgets/picker_wrapper_widget.dart

@@ -0,0 +1,61 @@
+import 'package:cake_wallet/utils/responsive_layout_util.dart';
+import 'package:flutter/material.dart';
+import 'package:cake_wallet/src/widgets/alert_background.dart';
+import 'package:cake_wallet/src/widgets/alert_close_button.dart';
+
+class PickerWrapperWidget extends StatelessWidget {
+  PickerWrapperWidget({required this.children, this.hasTitle = false});
+
+  final List<Widget> children;
+  final bool hasTitle;
+
+  @override
+  Widget build(BuildContext context) {
+    final double padding = 24;
+
+    final mq = MediaQuery.of(context);
+    final bottom = mq.viewInsets.bottom;
+    final height = mq.size.height - bottom;
+    final screenCenter = height / 2;
+
+    double closeButtonBottom = 60;
+    double containerHeight = height * 0.65;
+    if (bottom > 0) {
+      // increase a bit or it gets too squished in the top
+      containerHeight = height * 0.75;
+
+      final containerCenter = containerHeight / 2;
+      final containerBottom = screenCenter - containerCenter;
+
+      // position the close button right below the search container
+      closeButtonBottom = closeButtonBottom -
+          containerBottom + (!hasTitle ? padding : padding / 1.5);
+    }
+
+    return AlertBackground(
+      child: Column(
+        children: [
+          Expanded(
+            flex: 1,
+            child: Stack(
+              alignment: Alignment.center,
+              children: <Widget>[
+                Column(
+                  mainAxisSize: MainAxisSize.min,
+                  children: children,
+                ),
+                SizedBox(height: ResponsiveLayoutUtil.kPopupSpaceHeight),
+                AlertCloseButton(bottom: closeButtonBottom),
+              ],
+            ),
+          ),
+          // gives the extra spacing using MediaQuery.viewInsets.bottom
+          // to simulate a keyboard area
+          SizedBox(
+            height: bottom,
+          )
+        ],
+      ),
+    );
+  }
+}