Rewrite upgrade-simple to C++

src/CMakeLists.txt

@@ -195,7 +195,7 @@ configure_file(vitastor.pc.in vitastor.pc @ONLY)
 # vitastor-disk
 add_executable(vitastor-disk
 	disk_tool.cpp disk_simple_offsets.cpp
-	disk_tool_journal.cpp disk_tool_meta.cpp disk_tool_prepare.cpp disk_tool_resize.cpp disk_tool_udev.cpp disk_tool_utils.cpp
+	disk_tool_journal.cpp disk_tool_meta.cpp disk_tool_prepare.cpp disk_tool_resize.cpp disk_tool_udev.cpp disk_tool_utils.cpp disk_tool_upgrade.cpp
 	crc32c.c str_util.cpp ../json11/json11.cpp rw_blocking.cpp allocator.cpp ringloop.cpp blockstore_disk.cpp
 )
 target_link_libraries(vitastor-disk