common: refactor common library pt2 (#8588)

- remove common lib
- split settings, remove common-md
- move ipc interop/kb_layout to interop
- rename core -> settings, settings -> old_settings
- os-detect header-only; interop -> PowerToysInterop
- split notifications, move single-use headers where they're used
- winstore lib
- rename com utils
- rename Updating and Telemetry projects
- rename core -> settings-ui and remove examples folder
- rename settings-ui folder + consisent common/version include

src/settings-ui/Microsoft.PowerToys.Settings.UI.Library/SettingsRepository`1.cs

@@ -0,0 +1,70 @@
+// 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 Microsoft.PowerToys.Settings.UI.Library.Interfaces;
+
+namespace Microsoft.PowerToys.Settings.UI.Library
+{
+    // This Singleton class is a wrapper around the settings configurations that are accessed by viewmodels.
+    // This class can have only one instance and therefore the settings configurations are common to all.
+    public class SettingsRepository<T> : ISettingsRepository<T>
+        where T : class, ISettingsConfig, new()
+    {
+        private static readonly object _SettingsRepoLock = new object();
+
+        private static ISettingsUtils _settingsUtils;
+
+        private static SettingsRepository<T> settingsRepository;
+
+        private T settingsConfig;
+
+        // Suppressing the warning as this is a singleton class and this method is
+        // necessarily static
+#pragma warning disable CA1000 // Do not declare static members on generic types
+        public static SettingsRepository<T> GetInstance(ISettingsUtils settingsUtils)
+#pragma warning restore CA1000 // Do not declare static members on generic types
+        {
+            // To ensure that only one instance of Settings Repository is created in a multi-threaded environment.
+            lock (_SettingsRepoLock)
+            {
+                if (settingsRepository == null)
+                {
+                    settingsRepository = new SettingsRepository<T>();
+                    _settingsUtils = settingsUtils ?? throw new ArgumentNullException(nameof(settingsUtils));
+                }
+
+                return settingsRepository;
+            }
+        }
+
+        // The Singleton class must have a private constructor so that it cannot be instantiated by any other object other than itself.
+        private SettingsRepository()
+        {
+        }
+
+        // Settings configurations shared across all viewmodels
+        public T SettingsConfig
+        {
+            get
+            {
+                if (settingsConfig == null)
+                {
+                    T settingsItem = new T();
+                    settingsConfig = _settingsUtils.GetSettings<T>(settingsItem.GetModuleName());
+                }
+
+                return settingsConfig;
+            }
+
+            set
+            {
+                if (value != null)
+                {
+                    settingsConfig = value;
+                }
+            }
+        }
+    }
+}