feat: Properties 中添加默认 ExportHandler

[Ghostbaby]

现状： 对于不需要输出 map 的场景，需要支持跳过输出。

	config := &loader.Config{
		ObjectPath:  objectPath,
		Logger:      logger,
		PollTimeout: 100 * time.Millisecond,
		Properties: meta.Properties{
			Maps: map[string]*meta.Map{
				"global_version": {
					Name:          "global_version",
					ExportHandler: &SkipHandler{},
				},
				"events": {
					Name:          "events",
					ExportHandler: &SkipHandler{},
				},
				"prog_states": {
					Name:          "prog_states",
					ExportHandler: &SkipHandler{},
				},
				"pid_map_states": {
					Name:          "pid_map_states",
					ExportHandler: &SkipHandler{},
				},
				"pid_prog_states": {
					Name:          "map_states",
					ExportHandler: &SkipHandler{},
				},
				"stack_traces": {
					Name:          "stack_traces",
					ExportHandler: &SkipHandler{},
				},
			},
		},
	}