A preview call can be quite expensive and cause timeout in a cluster. As a short term fix we identified 2 (hopefully) small fixes:

- make the call cancellable, the main issue here seems to be that preview calls search without using a parent task id(see this fix for data feeds: https://github.com/elastic/elasticsearch/pull/88142/files#diff-aba58244cb8f9dfa3ac3b6efeb02259e3d5956576f56c1ff5e243dd2aac27381)
- pass the timeout parameter of the preview call to the search call, currently a timeout can be specified, but is ignored for the inner search call, which is executed with no timeout (see https://www.elastic.co/guide/en/elasticsearch/reference/master/search-search.html#search-search-api-query-params).

Both changes are bugs and shall be relatively simple to implement and considered for backport to the 7.17 branch.

@przemekwitek can you have a look at this?

related: #88010
x-pack/plugin/core/src/test/java/org/elasticsearch/xpack/core/transform/action/PreviewTransformActionRequestTests.java
"destination-field2": {
                    "terms": {
                      "field": "term-field"
                    }
                  }
                },
                "aggs": {
                  "avg_response": {
                    "avg": {
                      "field": "responsetime"
                    }
                  }
                }
              }
            }""", transformIdJson, destConfigJson));
        try (
            XContentParser parser = JsonXContent.jsonXContent.createParser(
                xContentRegistry(),
                DeprecationHandler.THROW_UNSUPPORTED_OPERATION,
                json.streamInput()
            )
        ) {
            Request request = Request.fromXContent(parser, AcknowledgedRequest.DEFAULT_ACK_TIMEOUT);
            assertThat(request.getConfig().getId(), is(equalTo(expectedTransformId)));
            assertThat(request.getConfig().getDestination().getIndex(), is(equalTo(expectedDestIndex)));
            assertThat(request.getConfig().getDestination().getPipeline(), is(equalTo(expectedDestPipeline)));
        }
    }
}