overlay: simplify various input controls by introducing new custom ImGUI widgets (#536)

## Description of change

* Add a red `x` button to replace `Clear` button in binding tabs
(Buttons/Analog/Lights).
* Add a gray `x` button to replace `Clear` button in options tabs next
to input widgets
* Add helper for truncating text and adding ellipsis (...) to deal with
text overflow in tables.
* Reword some UI text for clarity

src/spice2x/overlay/windows/config.h

@@ -88,6 +88,7 @@ namespace overlay::windows {
             Button *button,
             const GameAPI::Buttons::State button_state,
             const float button_velocity);
+        void clear_button(Button &button);
 
         void build_analogs(const std::string &name, std::vector<Analog> *analogs);
         void edit_analog_popup(Analog &analog);