**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/test/java/org/elasticsearch/action/admin/indices/rollover/TransportRolloverActionTests.java
final ClusterState stateBefore = ClusterState.builder(ClusterName.DEFAULT)
            .metadata(Metadata.builder().put(indexMetadata).put(indexMetadata2))
            .build();
        when(mockCreateIndexService.applyCreateIndexRequest(any(), any(), anyBoolean())).thenReturn(stateBefore);
        when(mdIndexAliasesService.applyAliasActions(any(), any())).thenReturn(stateBefore);
        MetadataRolloverService rolloverService = new MetadataRolloverService(
            mockThreadPool,
            mockCreateIndexService,
            mdIndexAliasesService,
            EmptySystemIndices.INSTANCE
        );
        final TransportRolloverAction transportRolloverAction = new TransportRolloverAction(
            mockTransportService,
            mockClusterService,
            mockThreadPool,
            mockActionFilters,
            mockIndexNameExpressionResolver,
            rolloverService,
            mockClient,
            mockAllocationService
        );
        
        
        PlainActionFuture<RolloverResponse> future = new PlainActionFuture<>();
        RolloverRequest rolloverRequest = new RolloverRequest("logs-alias", "logs-index-000003");
        rolloverRequest.addMaxIndexDocsCondition(500L);
        rolloverRequest.dryRun(true);
        transportRolloverAction.masterOperation(mock(Task.class), rolloverRequest, stateBefore, future);
        RolloverResponse response = future.actionGet();
        assertThat(response.getOldIndex(), equalTo("logs-index-000002"));