[Registry Preview] Moving to a different API to call the File Picker (#25260)

* Moving from FileOpenPicker

Moving from FileOpenPicker to a Win32/PInvoke version, so it can be opened while running as Admin.

* Update Resources.resw

Replacing a lost string.

* Save file picker also crashed

Switched to Win32-based SafeFilePicker
Cleaned up some of the code which should now pass spell checking and removed pragmas

src/modules/registrypreview/RegistryPreviewUI/FileName.cs

@@ -0,0 +1,39 @@
+// 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.Runtime.InteropServices;
+
+namespace RegistryPreview
+{
+    // Workaround for File Pickers that don't work while running as admin, per:
+    // https://github.com/microsoft/WindowsAppSDK/issues/2504
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
+    public struct FileName
+    {
+        public int StructSize;
+        public IntPtr HwndOwner;
+        public IntPtr Instance;
+        public string Filter;
+        public string CustomFilter;
+        public int MaxCustFilter;
+        public int FilterIndex;
+        public string File;
+        public int MaxFile;
+        public string FileTitle;
+        public int MaxFileTitle;
+        public string InitialDir;
+        public string Title;
+        public int Flags;
+        public short FileOffset;
+        public short FileExtension;
+        public string DefExt;
+        public IntPtr CustData;
+        public IntPtr Hook;
+        public string TemplateName;
+        public IntPtr PtrReserved;
+        public int Reserved;
+        public int FlagsEx;
+    }
+}