Replace our custom `OpenWithDlg()` with system `SHOpenWithDialog()`

[zufuliu]

Our custom open with dialog (from menu Tools -> Open Document With...):

System open with dialog (same as click "Open with..." context menu in Windows Explorer):

System dialog looks more useful, as it listed registered applications for current file extension.

--- a/src/Notepad4.cpp
+++ b/src/Notepad4.cpp
@@ -2825,7 +2825,10 @@ LRESULT MsgCommand(HWND hwnd, WPARAM wParam, LPARAM lParam) {
                if (bSaveBeforeRunningTools && !FileSave(FileSaveFlag_Ask)) {
                        break;
                }
-               OpenWithDlg(hwnd, szCurFile);
+               if (StrNotEmpty(szCurFile)) {
+                       const OPENASINFO info {szCurFile, nullptr, OAIF_ALLOW_REGISTRATION | OAIF_EXEC};
+                       SHOpenWithDialog(hwnd, &info);
+               }
                break;

[zufuliu]

Another option is adding a new menu "Open with Default Application", "Open with Associated Application", or something similar for system open with dialog, keeps "Open Document With..." as is.