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/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/Function.java
*
         * TODO: replace the boolean with a more descriptive enum.
         *
         * @param searchResponse the response after querying for changes
         * @return the position of the change collector, null in case the collector is exhausted
         */
        Map<String, Object> processSearchResponse(SearchResponse searchResponse);
        /**
         * Build the filter query to narrow the result set given the previously collected changes.
         *
         * @param lastCheckpoint the last checkpoint
         * @param nextCheckpoint the next (in progress) checkpoint
         * @return a filter query, null in case of no filter
         */
        QueryBuilder buildFilterQuery(TransformCheckpoint lastCheckpoint, TransformCheckpoint nextCheckpoint);
        /**
         * Filter indices according to the given checkpoints.
         *
         * @param lastCheckpoint the last checkpoint
         * @param nextCheckpoint the next (in progress) checkpoint
         * @return set of indices to query
         */
        Collection<String> getIndicesToQuery(TransformCheckpoint lastCheckpoint, TransformCheckpoint nextCheckpoint);
        /**
         * Clear the internal state to free up memory.
         */
        void clear();
        /**
         * Whether the collector optimizes change detection by narrowing the required query.
         *