Support converting hex strings to integers

[andrewkroh]

I would like to be able to convert hexadecimal numbers that are prefixed with 0x to integers with the Ingest Node convert processor. Sometimes Windows event logs contain hex values that I'd like to convert to numbers (such as the TargetProcessId in 4690).

For example, this pipeline results in a java.lang.IllegalArgumentException: unable to convert [0x01] to integer.

POST _ingest/pipeline/_simulate
{
  "pipeline": {
    "processors": [
      {
        "convert": {
          "field": "hex",
          "type": "integer"
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "hex": "0x01"
      }
    }
  ]
}

[elasticmachine]

Pinging @elastic/es-core-infra