use WIN_StringToUTF8W instead of WIN_StringToUTF8 where needed (#2)

cf. bug #5435.
- SDL_wasapi_win32.c (GetWasapiDeviceName): pwszVal is WCHAR*
- windows/SDL_sysfilesystem.c (SDL_GetBasePath, SDL_GetPrefPath)
- windows/SDL_sysurl.c (SDL_SYS_OpenURL): wurl is WCHAR*
- SDL_windowssensor.c (ConnectSensor): bstr_name is WCHAR*
- windows/SDL_systhread.c (SDL_SYS_SetupThread): strw is WCHAR*

src/thread/windows/SDL_systhread.c

@@ -170,7 +170,7 @@ SDL_SYS_SetupThread(const char *name)
         }
 
         if (pSetThreadDescription != NULL) {
-            WCHAR *strw = WIN_UTF8ToString(name);
+            WCHAR *strw = WIN_UTF8ToStringW(name);
             if (strw) {
                 pSetThreadDescription(GetCurrentThread(), strw);
                 SDL_free(strw);