MDEV-27525 Invalid (non-UTF8) characters found for option 'plugin_dir'

Two Problems
1. Upgrade wizard failed to retrieve path to service executable,
if it contained non-ASCII.
Fixed by setlocale(LC_ALL, "en_US.UTF8"), which was missing in upgrade wizard

2.mysql_upgrade_service only updated (converted to UTF8) the server's sections
leaving client's as-is

Corrected typo.

3. Fixed assertion in my_getopt, turns out to be too strict.

win/upgrade_wizard/upgradeDlg.cpp

@@ -15,6 +15,7 @@
 #include <vector>
 
 #include <winservice.h>
+#include <locale.h>
 
 using namespace std;
 
@@ -271,6 +272,11 @@ BOOL CUpgradeDlg::OnInitDialog()
 
   m_Progress.ShowWindow(SW_HIDE);
   m_Ok.EnableWindow(FALSE);
+  if (GetACP() == CP_UTF8)
+  {
+    /* Required for mbstowcs, used in some functions.*/
+    setlocale(LC_ALL, "en_US.UTF8");
+  }
   PopulateServicesList();
   return TRUE;  // return TRUE  unless you set the focus to a control
 }