DOCS-6280: Added saveState and restoreState fields in query explainer executionStats.

Author: nlarew

source/reference/explain-results.txt

@@ -182,6 +182,8 @@ information:
          "advanced" : <int>,
          "needTime" : <int>,
          "needYield" : <int>,
+         "saveState" : <int>,
+         "restoreState" : <int>,
          "isEOF" : <boolean>,
          ...
          "inputStage" : {
@@ -191,6 +193,8 @@ information:
             "executionTimeMillisEstimate" : <int>,
             "keysExamined" : <int>,
             "docsExamined" : <int>,
+            "saveState" : <int>,
+            "restoreState" : <int>,
             ...
             "inputStage" : {
                ...
@@ -274,8 +278,20 @@ information:
 
       .. data:: explain.executionStats.executionStages.needYield
 
-         The number of times that the storage layer requested that the query
-         system yield its locks.
+         The number of times that the storage layer requested that the
+         query stage suspend processing and yield its locks.
+
+      .. data:: explain.executionStats.executionStages.saveState
+
+         The number of times that the query stage suspended processing
+         and saved its current execution state, for example in
+         preparation for yielding its locks.
+
+      .. data:: explain.executionStats.executionStages.restoreState
+
+         The number of times that the query stage restored a saved
+         execution state, for example after recovering locks that it had
+         previously yielded.
 
       .. data:: explain.executionStats.executionStages.isEOF