data: Switch PW600-compatible devices over to the new generic 3 btn pen

From Huion's website [1]: Compatible with Kamvas Pro 19 and Kamvas Pro
27, Kamvas 16 (Gen 3) and Kamvas 13 (Gen 3)

This produces false positives if a user doesn't have that tool - we
still cannot identify Huion pens at runtime. But better to have
configuration for buttons that don't exist than lacking configurations
for buttons that do exist.

[1] https://store.huion.com/au/products/battery-free-pen-pw600

Assisted-by: Claude:claude-opus-4-6

Author: whot

data/huion-kamvas-13-gs1333.tablet

@@ -42,7 +42,7 @@ Width=305
 Height=178
 Layout=huion-kamvas-13-gs1333.svg
 IntegratedIn=Display
-Styli=@generic-no-eraser;
+Styli=@generic-3btn-with-eraser;
 
 [Features]
 Stylus=true

data/huion-kamvas-16-gs1563.tablet

@@ -44,7 +44,7 @@ Width=356
 Height=203
 Layout=huion-kamvas-16-gs1563.svg
 IntegratedIn=Display
-Styli=@generic-no-eraser;
+Styli=@generic-3btn-with-eraser;
 
 [Features]
 Stylus=true

data/huion-kamvas-pro-19-gt1902.tablet

@@ -18,7 +18,7 @@ DeviceMatch=usb|256c|006b||HUION_M220;
 # HUION_MAGIC_BYTES="1303803f01b8b300ff3fd81303000000080040"
 Width=406
 Height=229
-Styli=@generic-no-eraser;
+Styli=@generic-3btn-with-eraser;
 IntegratedIn=Display
 
 [Features]

data/huion-kamvas-pro-27-gt2701.tablet

@@ -13,7 +13,7 @@ ModelName=GT2701
 DeviceMatch=usb|256c|006c;
 Width=597
 Height=336
-Styli=@generic-no-eraser;
+Styli=@generic-3btn-with-eraser;
 IntegratedIn=Display
 
 [Features]

test/test_libwacom.py

@@ -333,6 +333,13 @@ def test_mobilestudio_pro_modeswitch(db):
                 WacomStylus.Generic.PEN_NO_ERASER,
             ],
         ],
+        [
+            (0x256C, 0x006C),
+            [
+                WacomStylus.Generic.PEN_3BTN_WITH_ERASER,
+                WacomStylus.Generic.ERASER_3BTN,
+            ],
+        ],
     ],
 )
 def test_generic_pens(db, usbid, expected):