[fxcop] Settings UI library (part 1) (#7187)

* Mark methods static and replace Count() with Length

* Use IsNullOrEmpty for null string checks

* Remove redundant initializations to default values

* Use nameof(property name) in place of string literals

* Add NativeMethods class

* Rename property getters in KeysDataModel & AppSpecificKeysDataModel

* Remove underscores from method names

* Mark Helper class static

* Address comments & typo fixes

* Add EncoderGuid property and fix failing build

* Update binding in GeneralPages.xaml

src/core/Microsoft.PowerToys.Settings.UI.Lib/Utilities/NativeMethods.cs

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Text;
+
+namespace Microsoft.PowerToys.Settings.UI.Lib.Utilities
+{
+    internal static class NativeMethods
+    {
+        [DllImport("user32.dll")]
+        public static extern bool AllowSetForegroundWindow(int dwProcessId);
+    }
+}