MDEV-26713 Treat codepage 65001 as utf8mb4, not utf8mb3

Also, fix the "UTF8" option in MSI, which is responsible for character-set-server
setting

mysys/charset.c

@@ -1393,7 +1393,7 @@ static const MY_CSET_OS_NAME charsets[] =
 #ifdef UNCOMMENT_THIS_WHEN_WL_WL_4024_IS_DONE
   {"cp54936",        "gb18030",  my_cs_exact},
 #endif
-  {"cp65001",        "utf8",     my_cs_exact},
+  {"cp65001",        "utf8mb4",  my_cs_exact},
 
 #else /* not Windows */
 

win/packaging/extra.wxs.in

@@ -461,7 +461,7 @@
             Section="mysqld"
             Name="my.ini"
             Key="character-set-server"
-            Value="utf8" />
+            Value="utf8mb4" />
       </Component>
 
       <!-- Shortcuts in program menu (mysql client etc) -->