BaseLine proto: Add query baseline supported metrics names. (#13005)

Author: wankai123

docs/en/changes/changes.md

@@ -65,6 +65,7 @@
 * OAP self observability: Add JVM heap and direct memory used metrics.
 * OAP self observability: Add watermark circuit break/recover metrics.
 * Add Baseline module for support alarm module query baseline data.
+* BaseLine: Support query baseline metrics names.
 
 #### UI
 

oap-server/metrics-baseline/src/main/proto/baseline.proto

@@ -19,14 +19,22 @@
 syntax = "proto3";
 package skywalking.baseline.v3;
 
+import "google/protobuf/empty.proto";
+
 option java_multiple_files = true;
 option java_package = "org.apache.skywalking.apm.baseline.v3";
 
 service AlarmBaselineService {
+    // Query the supported metrics names.
+    rpc querySupportedMetricsNames(google.protobuf.Empty) returns (AlarmBaselineMetricsNames);
     // Query the predicted metrics of the given service.
     rpc queryPredictedMetrics(AlarmBaselineRequest) returns (AlarmBaselineResponse);
 }
 
+message AlarmBaselineMetricsNames {
+    repeated string metricNames = 1;
+}
+
 // The request of the predicted metrics query.
 message AlarmBaselineRequest {
     // The request service metrics names.