overlay: address small polish issues (#543)

* Make a custom widget for truncated text that shows a tooltip only when
truncated
* Use the above widget more consistently in various places
* Ensure tooltips still show even when the preceding widget is disabled

src/spice2x/overlay/imgui/extensions.h

@@ -13,7 +13,7 @@ namespace ImGui {
     void Knob(float fraction, float size, float thickness = 2.f,
             float pos_x = -1.f, float pos_y = -1.f);
 
-    std::string TruncateText(const std::string& p_text, float p_truncated_width);
+    void TextTruncated(const std::string& p_text, float p_truncated_width);
     bool AddButton(const std::string& tooltip);
     bool DeleteButton(const std::string& tooltip);
     bool ClearButton(const std::string& tooltip);