**Elasticsearch version** (`bin/elasticsearch --version`): 7.16 (earlier too), 8.0, 8.1

**Description of the problem including expected versus actual behavior**:
Currently, the rollover requests are not cancellable, irrespective of the underlying incoming HTTP channel being closed (eg. by a proxy). This could result in clients receiving `504` and retrying the rollovers, resulting in multiple rollover operations being processed (some products issue rollovers without specifying conditions, so this could translate in multiple subsequent rollovers being executed).

This proposes using the `RestCancellableNodeClient` infrastructure for the rollover API, such that elasticsearch can react to the incoming HTTP connection being closed by cancelling the rollover operation.

server/src/main/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverAction.java
private final RolloverRequest rolloverRequest;
        private final IndicesStatsResponse statsResponse;
        private final RolloverResponse trialRolloverResponse;
        private final ActionListener<RolloverResponse> listener;
        private boolean clusterStateProcessed = false;
        
        
        
        private final SetOnce<String> sourceIndex = new SetOnce<>();
        private final SetOnce<String> rolloverIndex = new SetOnce<>();
        private final SetOnce<Map<String, Boolean>> conditionResults = new SetOnce<>();
        RolloverTask(
            RolloverRequest rolloverRequest,
            IndicesStatsResponse statsResponse,
            RolloverResponse trialRolloverResponse,
            ActionListener<RolloverResponse> listener
        ) {
            this.rolloverRequest = rolloverRequest;
            this.statsResponse = statsResponse;
            this.trialRolloverResponse = trialRolloverResponse;
            this.listener = listener;
        }
        ClusterState performRollover(ClusterState currentState) throws Exception {