Update integration tests to account for new explain command reply format

Needs additional updates to account for sharded clusters

JAVA-4169

Author: jyemin

driver-core/src/test/functional/com/mongodb/internal/operation/QueryOperationHelper.groovy

@@ -40,8 +40,8 @@ class QueryOperationHelper {
         } else if (winningPlan.containsKey('inputStage')) {
             return winningPlan.getDocument('inputStage').getDocument('keyPattern')
         } else if (winningPlan.containsKey('shards')) {
-            return winningPlan.getArray('shards')[0].asDocument().getDocument('winningPlan')
-                    .getDocument('inputStage').getDocument('keyPattern')
+            // recurse on shards[0] to get its query plan
+            return getKeyPattern(new BsonDocument('queryPlanner', winningPlan.getArray('shards')[0].asDocument()))
         }
     }
 }

driver-legacy/src/test/functional/com/mongodb/DBCursorFunctionalSpecification.groovy

@@ -274,7 +274,12 @@ class DBCursorFunctionalSpecification extends FunctionalSpecification {
         } else if (explainPlan.queryPlanner.winningPlan.inputStage != null) {
             return explainPlan.queryPlanner.winningPlan.inputStage.keyPattern
         } else if (explainPlan.queryPlanner.winningPlan.shards != null) {
-            return explainPlan.queryPlanner.winningPlan.shards[0].winningPlan.inputStage.keyPattern
+            def winningPlan = explainPlan.queryPlanner.winningPlan.shards[0].winningPlan
+            if (winningPlan.queryPlan?.inputStage != null) {
+                return winningPlan.queryPlan.inputStage.keyPattern
+            } else if (winningPlan.inputStage != null) {
+                return winningPlan.inputStage.keyPattern
+            }
         }
     }
 }