Transforms can be configured to search incredibly broad index patterns. These cause the lower level actions used by transforms to iterate huge numbers of shards unless measures are taken to restrict which shards are considered using information available in cluster state.

Anywhere where transforms calls an action that iterates shards it must use the `index_filter` functionality of that action to reduce scope. Calls to be changed:

- [x] Field caps
- [x] Creating PIT readers - requires #99740 be implemented as a pre-requisite
x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/transforms/ClientTransformIndexer.java
listener.onFailure(e);
                    return;
                }
                
                
                if (unwrappedException instanceof ActionNotFoundTransportException) {
                    logger.warn(
                        "[{}] source does not support point in time reader, falling back to normal search (more resource intensive)",
                        getJobId()
                    );
                    auditor.warning(
                        getJobId(),
                        "Source does not support point in time reader, falling back to normal search (more resource intensive)"
                    );
                    disablePit = true;
                } else {
                    logger.warn(
                        () -> format("[%s] Failed to create a point in time reader, falling back to normal search.", getJobId()),
                        e
                    );
                }
                listener.onResponse(namedSearchRequest);
            })
        );
    }
    void doSearch(Tuple<String, SearchRequest> namedSearchRequest, ActionListener<SearchResponse> listener) {
        String name = namedSearchRequest.v1();
        SearchRequest searchRequest = namedSearchRequest.v2();
        
        if (searchRequest.indices().length == 0) {