[ML] BWC tests for job_stats.timing_stats field (#43267)

Author: przemekwitek

x-pack/qa/rolling-upgrade/src/test/resources/rest-api-spec/test/mixed_cluster/30_ml_jobs_crud.yml

@@ -35,6 +35,20 @@
         job_id: old-cluster-job
   - match: { count: 1 }
 
+---
+"Test get old cluster job's timing stats":
+  - do:
+      ml.get_job_stats:
+        job_id: old-cluster-job
+  - match: { jobs.0.job_id: old-cluster-job }
+  - match: { jobs.0.state: "closed" }
+  - match: { jobs.0.timing_stats.job_id: old-cluster-job }
+  - match: { jobs.0.timing_stats.bucket_count: 1 }
+  - gte:   { jobs.0.timing_stats.minimum_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.maximum_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.average_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.exponential_average_bucket_processing_time_ms: 0.0 }
+
 ---
 "Test get old cluster categorization job":
   - do:

x-pack/qa/rolling-upgrade/src/test/resources/rest-api-spec/test/upgraded_cluster/30_ml_jobs_crud.yml

@@ -109,6 +109,20 @@ setup:
         name: ".ml-state-write"
   - is_true: ''
 
+---
+"Test get old cluster job's timing stats":
+  - do:
+      ml.get_job_stats:
+        job_id: old-cluster-job
+  - match: { jobs.0.job_id: old-cluster-job }
+  - match: { jobs.0.state: "closed" }
+  - match: { jobs.0.timing_stats.job_id: old-cluster-job }
+  - match: { jobs.0.timing_stats.bucket_count: 1 }
+  - gte:   { jobs.0.timing_stats.minimum_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.maximum_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.average_bucket_processing_time_ms: 0.0 }
+  - gte:   { jobs.0.timing_stats.exponential_average_bucket_processing_time_ms: 0.0 }
+
 ---
 "Test job with pre 6.4 rules":