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/common/notifications/BackgroundActivator/BackgroundHandler.idl

@@ -0,0 +1,10 @@
+namespace BackgroundActivator
+{
+    [version(1)]
+    runtimeclass BackgroundHandler
+    {
+        BackgroundHandler();
+    
+        void Run(Windows.ApplicationModel.Background.IBackgroundTaskInstance taskInstance);
+    }
+}