UI defaults:

- moved some common properties from FlatLightLaf.properties and FlatDarkLaf.properties to FlatLaf.properties
- use color functions for more properties

flatlaf-testing/src/main/resources/com/formdev/flatlaf/testing/FlatTestLaf.properties

@@ -32,6 +32,12 @@
 @cellFocusColor = #f00
 @icon = #afafaf
 
+# for buttons within components (e.g. combobox or spinner)
+@buttonArrowColor = #666
+@buttonDisabledArrowColor = #ABABAB
+@buttonHoverArrowColor = #f00
+@buttonPressedArrowColor = #00f
+
 @dropCellBackground = #f00
 @dropCellForeground = #0f0
 @dropLineColor = #00f
@@ -118,10 +124,6 @@ CheckBox.icon.pressedBackground = #FFC800
 ComboBox.background = #fff
 ComboBox.buttonBackground = #f0f0f0
 ComboBox.buttonEditableBackground = #ccc
-ComboBox.buttonArrowColor = #666
-ComboBox.buttonDisabledArrowColor = #ABABAB
-ComboBox.buttonHoverArrowColor = #f00
-ComboBox.buttonPressedArrowColor = #00f
 
 
 #---- Component ----