util: move ArrayReverse into package of its own

Leave just uint160 and uint256 types in util.

pkg/util/slice/array_test.go

@@ -0,0 +1,45 @@
+package slice
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var testCases = []struct {
+	arr []byte
+	rev []byte
+}{
+	{
+		arr: []byte{},
+		rev: []byte{},
+	},
+	{
+		arr: []byte{0x01},
+		rev: []byte{0x01},
+	},
+	{
+		arr: []byte{0x01, 0x02, 0x03, 0x04},
+		rev: []byte{0x04, 0x03, 0x02, 0x01},
+	},
+	{
+		arr: []byte{0x01, 0x02, 0x03, 0x04, 0x05},
+		rev: []byte{0x05, 0x04, 0x03, 0x02, 0x01},
+	},
+}
+
+func TestCopyReverse(t *testing.T) {
+	for _, tc := range testCases {
+		arg := make([]byte, len(tc.arr))
+		copy(arg, tc.arr)
+
+		have := CopyReverse(arg)
+		require.Equal(t, tc.rev, have)
+
+		// test that argument was copied
+		for i := range have {
+			have[i] = ^have[i]
+		}
+		require.Equal(t, tc.arr, arg)
+	}
+}