Fix login prompt not accepting input immediately

When trying to login, the currently selected textbox will not immediately accept input. It will only accept input after it is deselected and re-selected (pushing up then down)

The fix here is patching uMenu::SetSelected to call the previous menu item deselect and the new current menu item select function, also making this function more useful to be used elsewhere more.

Originally part of my menu mouse patch, cherry-picking from that so this bug can be fixed now (since it has already been 4 months since I last touched that...)