[BUG] PPL head limit and SQL limit offset throw exception

[penghuo]

What is the bug?

###
POST {{baseUrl}}/_plugins/_ppl
Content-Type: application/x-ndjson

{
  "query": "source = people"
}

###
POST {{baseUrl}}/_plugins/_ppl/_explain
Content-Type: application/x-ndjson

{
  "query": "source = people | head 1 from 1"
}

• error message

{
  "error": {
    "reason": "Invalid SQL query",
    "details": "Validation Failed: 1: using [from] is not allowed in a scroll context;2: [size] cannot be [0] in a scroll context;",
    "type": "ActionRequestValidationException"
  },
  "status": 400
}

How can one reproduce the bug?

###
PUT {{baseUrl}}/_plugins/_query/settings
Content-Type: application/x-ndjson

{
  "transient" : {
    "plugins.query.size_limit" : 1
  }
}

###
PUT {{baseUrl}}/people/_settings
Content-Type: application/x-ndjson

{
  "index": {
    "max_result_window": 1
  }
}

What is the expected behavior?
No exception.

[dblock]

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