Provide query statistics for apoc.merge functions

[process0]

Feature description

Currently apoc.merge.node and apoc.merge.relationship functions do not return any query statistics. These functions are often used in UNWIND $data .. queries where the user wants the ability to dynamically create the node and/or relationship label.

These functions generate and execute cypher statements from their inputs, so it should be possible to provide query statistics for them.

Related #1815

Considered alternatives

None that I am aware of

How this feature can improve the project?

It will provide accurate statistics of the queries run. The current statistics returned are 0 for every SummaryCounter field e.g.:

  "counters": {
    "_stats": {
      "nodesCreated": 0,
      "nodesDeleted": 0,
      "relationshipsCreated": 0,
      "relationshipsDeleted": 0,
      "propertiesSet": 0,
      "labelsAdded": 0,
      "labelsRemoved": 0,
      "indexesAdded": 0,
      "indexesRemoved": 0,
      "constraintsAdded": 0,
      "constraintsRemoved": 0
    },
    "_systemUpdates": 0
  },
  "updateStatistics": {
    "_stats": {
      "nodesCreated": 0,
      "nodesDeleted": 0,
      "relationshipsCreated": 0,
      "relationshipsDeleted": 0,
      "propertiesSet": 0,
      "labelsAdded": 0,
      "labelsRemoved": 0,
      "indexesAdded": 0,
      "indexesRemoved": 0,
      "constraintsAdded": 0,
      "constraintsRemoved": 0
    },
    "_systemUpdates": 0
  },