[fxcop] Settings UI library (part 2) (#7257)

* Suppress warnings for read-only collection properties (see code comments)

* Call ConfigureAwait on tasks

* Add CultureInfo and StringComparison policy for certain string operations

* Add checks and exceptions for null arguments to public methods

* Rename RaisePropertyChanged to NotifyPropertyChanged

* Suppress CA1000 warning on SettingsRepository class

* Implement Disposable pattern in HotkeySettingsControlHook

* Modify null argument handling in KeyboardManagerViewModel::CombineShortcutLists

src/core/Microsoft.PowerToys.Settings.UI.Lib/PowerLauncherSettings.cs

@@ -2,6 +2,7 @@
 // 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.Text.Json;
 using System.Text.Json.Serialization;
 using Microsoft.PowerToys.Settings.UI.Lib.Interface;
@@ -30,6 +31,11 @@ namespace Microsoft.PowerToys.Settings.UI.Lib
                 WriteIndented = true,
             };
 
+            if (settingsUtils == null)
+            {
+                throw new ArgumentNullException(nameof(settingsUtils));
+            }
+
             settingsUtils.SaveSettings(JsonSerializer.Serialize(this, options), ModuleName);
         }