CDRIVER-5770 Convert retryable write command construction prose tests to spec tests (#1800)

* sync spec tests to 11022ca

* remove extra `bson_destroy`

The `bson_t` is allocated with `tmp_bson`. Destroying results in a double free when the test runner destroys temporary `bson_t`.

* make failure to clean up failpoints terminate tests

* create internal mongo client after possibly modifying URI

* use single mongos for handling initialData

* use primary, not primaryPreferred, read preference

To match spec.

Author: kevinAlbs

src/libmongoc/tests/json/retryable_writes/unified/aggregate-out-merge.json

@@ -0,0 +1,144 @@
+{
+  "description": "aggregate with $out/$merge does not set txnNumber",
+  "schemaVersion": "1.3",
+  "runOnRequirements": [
+    {
+      "minServerVersion": "3.6",
+      "topologies": [
+        "replicaset",
+        "sharded",
+        "load-balanced"
+      ]
+    }
+  ],
+  "createEntities": [
+    {
+      "client": {
+        "id": "client0",
+        "observeEvents": [
+          "commandStartedEvent"
+        ]
+      }
+    },
+    {
+      "database": {
+        "id": "database0",
+        "client": "client0",
+        "databaseName": "retryable-writes-tests"
+      }
+    },
+    {
+      "collection": {
+        "id": "collection0",
+        "database": "database0",
+        "collectionName": "coll0"
+      }
+    }
+  ],
+  "initialData": [
+    {
+      "collectionName": "mergeCollection",
+      "databaseName": "retryable-writes-tests",
+      "documents": []
+    }
+  ],
+  "tests": [
+    {
+      "description": "aggregate with $out does not set txnNumber",
+      "operations": [
+        {
+          "object": "collection0",
+          "name": "aggregate",
+          "arguments": {
+            "pipeline": [
+              {
+                "$sort": {
+                  "x": 1
+                }
+              },
+              {
+                "$match": {
+                  "_id": {
+                    "$gt": 1
+                  }
+                }
+              },
+              {
+                "$out": "outCollection"
+              }
+            ]
+          }
+        }
+      ],
+      "expectEvents": [
+        {
+          "client": "client0",
+          "events": [
+            {
+              "commandStartedEvent": {
+                "commandName": "aggregate",
+                "command": {
+                  "txnNumber": {
+                    "$$exists": false
+                  }
+                }
+              }
+            }
+          ]
+        }
+      ]
+    },
+    {
+      "description": "aggregate with $merge does not set txnNumber",
+      "runOnRequirements": [
+        {
+          "minServerVersion": "4.1.11"
+        }
+      ],
+      "operations": [
+        {
+          "object": "collection0",
+          "name": "aggregate",
+          "arguments": {
+            "pipeline": [
+              {
+                "$sort": {
+                  "x": 1
+                }
+              },
+              {
+                "$match": {
+                  "_id": {
+                    "$gt": 1
+                  }
+                }
+              },
+              {
+                "$merge": {
+                  "into": "mergeCollection"
+                }
+              }
+            ]
+          }
+        }
+      ],
+      "expectEvents": [
+        {
+          "client": "client0",
+          "events": [
+            {
+              "commandStartedEvent": {
+                "commandName": "aggregate",
+                "command": {
+                  "txnNumber": {
+                    "$$exists": false
+                  }
+                }
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}