PowerToys Run cache issue (#4472)

* Clean termination of powertoys process.

* Fixed issue with run not responding to WM_CLOSE

* Fixed serialization error in pinyin and image cache

* Fixed merge conflict

* Fixed nit wrt to master

* Fixed undeterministic behaviour of Environment.Exit function

* Update timing for terminate process

src/core/Microsoft.PowerToys.Settings.UI.Runner/Program.cs

@@ -58,7 +58,9 @@ namespace Microsoft.PowerToys.Settings.UI.Runner
                         IsUserAnAdmin = false;
                     }
 
-                    RunnerHelper.WaitForPowerToysRunner(PowerToysPID);
+                    RunnerHelper.WaitForPowerToysRunner(PowerToysPID, () => {
+                        Environment.Exit(0);
+                    });
 
                     ipcmanager = new TwoWayPipeMessageIPCManaged(args[1], args[0], null);
                     ipcmanager.Start();