feat: Support export metric in remote write format (#2928)

* feat: remote write metric task

* chore: pass stanalone task to frontend

* chore: change name to system metric

* fix: add header and rename to export metrics

tests-integration/tests/http.rs

@@ -753,6 +753,13 @@ timeout = "10s"
 connect_timeout = "1s"
 tcp_nodelay = true
 
+[frontend.export_metrics]
+enable = false
+db = ""
+write_interval = "30s"
+
+[frontend.export_metrics.headers]
+
 [datanode]
 mode = "standalone"
 node_id = 0
@@ -809,6 +816,13 @@ parallel_scan_channel_size = 32
 [datanode.logging]
 enable_otlp_tracing = false
 
+[datanode.export_metrics]
+enable = false
+db = ""
+write_interval = "30s"
+
+[datanode.export_metrics.headers]
+
 [logging]
 enable_otlp_tracing = false"#,
         store_type,