Fix TAB handling for controls with wxTE_PROCESS_ENTER in wxMSW

When this style is specified, TAB has to be handled manually as well and
we do it by calling our Navigate() method explicitly. But for it to work
correctly we need to pretend that it's called in response to a real TAB
press by specifying FromTab flag and the code forgot to do this -- just
add the missing flag to fix it now.

In particular, this ensures that the special code handling radio buttons
in wxControlContainer::HandleOnNavigationKey() is really executed and
fixes a bug with pressing TAB on a wxTextCtrl with wxTE_PROCESS_ENTER
before a radio button group would select the first radio button of this
group instead of jumping to the currently selected button.

Closes #18392.

src/msw/textctrl.cpp

@@ -2080,7 +2080,7 @@ void wxTextCtrl::OnChar(wxKeyEvent& event)
             {
                 if ( ::GetFocus() == GetHwnd() )
                 {
-                    int flags = 0;
+                    int flags = wxNavigationKeyEvent::FromTab;
                     if (!event.ShiftDown())
                         flags |= wxNavigationKeyEvent::IsForward ;
                     if (event.ControlDown())