Use custom action key icon

1. get icon from getKeyboardSettingsFeatureProvider
2. set color for it

Bug: 269214138
Test: manual, atest KeyboardSettingsFeatureProviderImplTest
Change-Id: I3a2d47e8230aec1404300b000e8b1fcf221e2a65

src/com/android/settings/inputmethod/KeyboardSettingsFeatureProviderImpl.java

@@ -17,6 +17,7 @@
 package com.android.settings.inputmethod;
 
 import android.content.Context;
+import android.graphics.drawable.Drawable;
 
 import androidx.preference.PreferenceScreen;
 
@@ -34,4 +35,9 @@ public class KeyboardSettingsFeatureProviderImpl implements KeyboardSettingsFeat
     public boolean addFirmwareUpdateCategory(Context context, PreferenceScreen screen) {
         return false;
     }
+
+    @Override
+    public Drawable getActionKeyIcon(Context context) {
+        return null;
+    };
 }