shared/helpers: use ARRAY_COPY where possible

In "backend-drm: simplify compile time array copy", ARRAY_COPY was
introduced to be used by the DRM-backend.

In this patch we expand its usage to other code where hardcoded arrays
are being copied.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>

tests/vertex-clip-test.c

@@ -176,8 +176,8 @@ static void
 deep_copy_polygon8(const struct polygon8 *src, struct polygon8 *dst)
 {
 	dst->n = src->n;
-	memcpy((void *) dst->x, src->x, sizeof (src->x));
-	memcpy((void *) dst->y, src->y, sizeof (src->y));
+	ARRAY_COPY(dst->x, src->x);
+	ARRAY_COPY(dst->y, src->y);
 }
 
 TEST_P(clip_polygon_n_vertices_emitted, test_data)