BUGFIX: Retry on conflict also in fulltext method and make number of retries configurable

[gradinarufelix]

We had issues (see below) with version conflicts in ElasticSearch. We first noticed it after a major ES version upgrade on our server. And I think I finally found a solution. One the one hand by adding retryOnConflict parameter also in the fulltext method, but also by making the number of retries configurable.

As far as I understand this is happening, because the painless script increases the ES document version, which leads the following the request to fail, even though there is no real concurrency.

{
    "update": {
        "_index": "xxx-production-default-1748641843",
        "_type": "_doc",
        "_id": "0c32c7170b89614b754749aceb810a0649d9ccb4",
        "status": 409,
        "error": {
            "type": "version_conflict_engine_exception",
            "reason": "[0c32c7170b89614b754749aceb810a0649d9ccb4]: version conflict, required seqNo [49036], primary term [1]. current document has seqNo [49039] and primary term [1]",
            "index_uuid": "-1GzR6SVSASUgeS_xdPXnQ",
            "shard": "0",
            "index": "xxx-production-default-1748641843"
        }
    }
}