[BUG] GetStats class serializes the time field as getTime in XContent/JSON

[Xtansia]

Describe the bug

The GetStats class serializes what should be the time field as getTime instead.

This issue was introduced in a refactoring from nearly twelve years ago (ie. very pre-fork) where a find & replace appears to have gone awry: cc83c2f#diff-f7abcc8f5eb3ec75bb9be11b7fe88baa0bcedf62c3c481552a0e98ceb7125a27R124

This means that when getting stats for an index, the "human" variant of time_in_millis becomes getTime rather than just time as expected.

Related component

Other

To Reproduce

1. Create an empty index: PUT /movies
2. Get stats for the index enabling the "human" fields: GET /movies/_stats?human&filter_path=_all.primaries.get
3. See response:

{
  "_all": {
    "primaries": {
      "get": {
        "total": 0,
        "getTime": "0s",
        "time_in_millis": 0,
        "exists_total": 0,
        "exists_time": "0s",
        "exists_time_in_millis": 0,
        "missing_total": 0,
        "missing_time": "0s",
        "missing_time_in_millis": 0,
        "current": 0
      }
    }
  }
}

Expected behavior

The getTime field should be named simply time to align with all other "human" _in_millis pairings.

Additional Details

Screenshots