ESQL does not support cross-cluster search yet; when a CCS pattern is used in a FROM command, the error message is not very clear for the end user

<img width="590" alt="Screenshot 2023-11-27 alle 15 38 02" src="https://github.com/elastic/elasticsearch/assets/459289/5af48932-4a4c-416a-a926-7bd486d282a5">

We should make it more user friendly
x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plugin/ComputeService.java
CountDown countDown = new CountDown(targetShards.size());
            for (IndexShard targetShard : targetShards) {
                targetShard.ensureShardSearchActive(ignored -> {
                    if (countDown.countDown()) {
                        ActionListener.completeWith(listener, () -> {
                            final List<SearchContext> searchContexts = new ArrayList<>(targetShards.size());
                            boolean success = false;
                            try {
                                for (IndexShard shard : targetShards) {
                                    var aliasFilter = aliasFilters.getOrDefault(shard.shardId().getIndex(), AliasFilter.EMPTY);
                                    ShardSearchRequest shardSearchLocalRequest = new ShardSearchRequest(shard.shardId(), 0, aliasFilter);
                                    SearchContext context = searchService.createSearchContext(
                                        shardSearchLocalRequest,
                                        SearchService.NO_TIMEOUT
                                    );
                                    searchContexts.add(context);
                                }
                                for (SearchContext searchContext : searchContexts) {
                                    searchContext.preProcess();
                                }
                                success = true;
                                return searchContexts;
                            } finally {
                                if (success == false) {
                                    IOUtils.close(searchContexts);
                                }
                            }
                        });
                    }
                });