LibGUI: Give some widgets a reasonable default fixed height

Instead of hard-coding 22 in random places, just make the following
widgets have a fixed height of 22 by default: Button, CheckBox,
ColorInput, ComboBox, RadioButton, SpinBox, TextBox.

In the future we can make this relative to the current font size,
but for now at least this centralizes the setting a bit better.

Libraries/LibGUI/ComboBox.cpp

@@ -58,6 +58,8 @@ private:
 
 ComboBox::ComboBox()
 {
+    set_fixed_height(22);
+
     m_editor = add<ComboBoxEditor>();
     m_editor->set_frame_thickness(0);
     m_editor->on_return_pressed = [this] {