feat: selfmonitor metrics support dynamic labels and gc

[shunjiazhu]

Change-Id: I74af3156bbc37e047cfc7f7b6c26a807973aceb5

1. 自监控API，支持在打点时动态的传入TagValue，用于观测在插件初始化时无法确定label value的场景，比如http code等。

// ExportMetricRecords exports all metrics bound to this metric record.
// The results may be a list of map[string]string, each map[string]string is a set of measurements has the same labels.
// for example:
// []{
// {"counters":"{\"http_flusher_dropped_events\":\"3.0000\",\"http_flusher_flush_failure_count\":\"6.0000\",\"http_flusher_matched_events\":\"1.0000\",\"http_flusher_retry_count\":\"5.0000\",\"http_flusher_unmatched_events\":\"2.0000\"}","gauges":"{\"http_flusher_flush_latency_ns\":\"7.0000\"}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\"}"}
// {"counters":"{\"http_flusher_status_code_count\":\"8.0000\"}","gauges":"{}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\",\"status_code\":\"200\"}"}
// {"counters":"{\"http_flusher_status_code_count\":\"9.0000\"}","gauges":"{}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\",\"status_code\":\"400\"}"}
// {"counters":"{\"http_flusher_error_count\":\"10.0000\"}","gauges":"{}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\",\"level\":\"error\",\"reason\":\"timeout\"}"}
// {"counters":"{\"http_flusher_error_count\":\"11.0000\"}","gauges":"{}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\",\"level\":\"warn\",\"reason\":\"retry\"}"}
// {"counters":"{\"http_flusher_error_count\":\"12.0000\"}","gauges":"{}","labels":"{\"PluginId\":\"13\",\"PluginType\":\"flusher_http\",\"RemoteURL\":\"http://localhost:8081\",\"level\":\"error\",\"reason\":\"dropped\"}"}
// }
// Note:
// A metric may have three levels of labels
// 1. MetricsRecord Level Const Labels, like PluginType=flusher_http, PluginId=1
// 2. Metric Level Const Labels, for example, flusher_http may have a const label: RemoteURL=http://aliyun.com/write
// 3. Metric Level Dynamic Labels, like status_code=200, status_code=204

2. 自监控支持序列过期，当一个指标的一个特定的Tags组合长期没有打点时，允许其gc掉，防止因为内存中常驻维度过高而产生的内存开销。

	cumulativeCounter := NewCumulativeCounterMetricVector("test", constLabels, getTagNames(allTags),
		WithExpiration(time.Hour),
		WithCardinalityLimit(1000),
	)