feat: export go metrics to cpp

[Takuka0311]

基于 pr https://github.com/alibaba/ilogtail/pull/1453 拆分出的一部分，作用是把go的指标传输到了cpp 对go export出的指标格式进行了修改，但label keys、metric name什么还没有跟C++统一。

原格式：

{
    "child_node_id": "2",
    "config_name": "##1.0##xuanyang-test$collect-self-logs-go",
    "logstore": "",
    "node_id": "1",
    "plugin_id": "4",
    "plugin_name": "processor_regex",
    "project": "",
    "__name__": "proc_in_records_total",
    "proc_in_records_total": "29.0000"
}
{
    "child_node_id": "2",
    "config_name": "##1.0##xuanyang-test$collect-self-logs-go",
    "logstore": "",
    "node_id": "1",
    "plugin_id": "4",
    "plugin_name": "processor_regex",
    "project": "",
    "__name__": "proc_out_records_total",
    "proc_out_records_total": "29.0000"
}
{
    "child_node_id": "2",
    "config_name": "##1.0##xuanyang-test$collect-self-logs-go",
    "logstore": "",
    "node_id": "1",
    "plugin_id": "4",
    "plugin_name": "processor_regex",
    "project": "",
    "__name__": "proc_time_ms",
    "proc_time_ms": "0.0000"
}

现格式

{
    "label.child_node_id": "2",
    "label.config_name": "##1.0##xuanyang-test$collect-self-logs-go",
    "label.logstore": "",
    "label.node_id": "1",
    "label.plugin_id": "4",
    "label.plugin_name": "processor_regex",
    "label.project": "",
    "value.proc_in_records_total": "29.0000",
    "value.proc_out_records_total": "29.0000",
    "value.proc_time_ms": "0.0000"
}