quote watermark column with non-zero NumPartitionsOverride

[alon-zeltser-cyera]

Fix an issue of using PostgreSQL watermark column that contain uppercase letters for example

  "watermarkColumn": "rowInsertedAt",

and setting snapshotNumPartitionsOverride > 0, GetQRepPartitions fails with

{
  "message": "failed to get partitions from source: ERROR: column \"rowinsertedat\" does not exist (SQLSTATE 42703)",
  "source": "GoSDK",
  "cause": {
    "message": "ERROR: column \"rowinsertedat\" does not exist (SQLSTATE 42703)",
    "source": "GoSDK",
    "applicationFailureInfo": {
      "type": "PgError"
    }
  },
  "applicationFailureInfo": {
    "type": "wrapError"
  }
}

[CLAassistant]

All committers have signed the CLA.