pbio/image: Add Image test.

Add unit tests for image drawing. Test fill and line drawing.

Refs: pybricks/support#2154

Author: schodet

lib/pbio/platform/test/pbioconfig.h

@@ -3,6 +3,7 @@
 #define PBIO_CONFIG_DCMOTOR                 (1)
 #define PBIO_CONFIG_DCMOTOR_NUM_DEV         (6)
 #define PBIO_CONFIG_DRIVEBASE_SPIKE         (0)
+#define PBIO_CONFIG_IMAGE                   (1)
 #define PBIO_CONFIG_IMU                     (0)
 #define PBIO_CONFIG_LIGHT                   (1)
 #define PBIO_CONFIG_LOGGER                  (1)