Improve build scan tags and values for Jenkins matrix jobs (#50881)

gradle/build-scan.gradle

@@ -3,8 +3,7 @@ import org.gradle.initialization.BuildRequestMetaData
 
 import java.util.concurrent.TimeUnit
 
-
-long startTime = project.gradle.services.get(BuildRequestMetaData.class).getStartTime()
+long startTime = project.gradle.services.get(BuildRequestMetaData).getStartTime()
 
 buildScan {
   URL jenkinsUrl = System.getenv('JENKINS_URL') ? new URL(System.getenv('JENKINS_URL')) : null
@@ -14,18 +13,14 @@ buildScan {
   String nodeName = System.getenv('NODE_NAME')
 
   tag OS.current().name()
-  if (jobName) {
-    value 'Job name', jobName
-  }
-  if (buildNumber) {
-    value 'Job number', buildNumber
-  }
 
+  // Automatically publish scans from Elasticsearch CI
   if (jenkinsUrl?.host?.endsWith('elastic.co')) {
     publishAlways()
     buildScan.server = 'https://gradle-enterprise.elastic.co'
   }
 
+  // Link to Jenkins worker logs and system metrics
   if (nodeName) {
     link 'System logs', "https://infra-stats.elastic.co/app/infra#/logs?" +
       "&logFilter=(expression:'host.name:${nodeName}',kind:kuery)"
@@ -39,10 +34,26 @@ buildScan {
 
   // Jenkins-specific build scan metadata
   if (jenkinsUrl) {
+    // Parse job name in the case of matrix builds
+    // Matrix job names come in the form of "base-job-name/matrix_param1=value1,matrix_param2=value2"
+    def splitJobName = jobName.split('/')
+    if (splitJobName.length == 2) {
+      tag splitJobName[0]
+      tag splitJobName[1]
+      value 'Job Name', splitJobName[0]
+      def matrixParams = splitJobName[1].split(',')
+      matrixParams.collect { it.split('=') }.each { param ->
+        value "MATRIX_${param[0].toUpperCase()}", param[1]
+      }
+    } else {
+      tag jobName
+      value 'Job Name', jobName
+    }
+
     tag 'CI'
-    tag jobName
     link 'Jenkins Build', buildUrl
     link 'GCP Upload', "https://console.cloud.google.com/storage/elasticsearch-ci-artifacts/jobs/${jobName}/build/${buildNumber}.tar.bz2"
+    value 'Job Number', buildNumber
 
     System.getenv().getOrDefault('NODE_LABELS', '').split(' ').each {
       value 'Jenkins Worker Label', it