Downsampling is broken. Not sure why yet (likely caused by #97557). Invoking the downsample api results into:

```
org.elasticsearch.ElasticsearchSecurityException: no indices permissions found
        at org.elasticsearch.xpack.core.security.support.Exceptions.authorizationError(Exceptions.java:32) ~[?:?]
        at org.elasticsearch.xpack.core.security.authz.accesscontrol.SecurityIndexReaderWrapper.getIndicesAccessControl(SecurityIn
dexReaderWrapper.java:110) ~[?:?]
        at org.elasticsearch.xpack.core.security.authz.accesscontrol.SecurityIndexReaderWrapper.apply(SecurityIndexReaderWrapper.j
ava:76) ~[?:?]
        at org.elasticsearch.xpack.core.security.authz.accesscontrol.SecurityIndexReaderWrapper.apply(SecurityIndexReaderWrapper.j
ava:46) ~[?:?]
        at org.elasticsearch.index.shard.IndexShard.wrapSearcher(IndexShard.java:1590) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at org.elasticsearch.index.shard.IndexShard.wrapSearcher(IndexShard.java:1561) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at org.elasticsearch.index.engine.Engine$SearcherSupplier.acquireSearcher(Engine.java:1321) ~[elasticsearch-8.11.0-SNAPSHO
T.jar:?]
        at org.elasticsearch.index.engine.Engine.acquireSearcher(Engine.java:774) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at org.elasticsearch.index.shard.IndexShard.acquireSearcher(IndexShard.java:1549) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at org.elasticsearch.xpack.downsample.DownsampleShardIndexer.<init>(DownsampleShardIndexer.java:115) ~[?:?]
        at org.elasticsearch.xpack.downsample.DownsampleShardPersistentTaskExecutor.startDownsampleShardIndexer(DownsampleShardPersistentTaskExecutor.java:111) ~[?:?]
        at org.elasticsearch.xpack.downsample.DownsampleShardPersistentTaskExecutor$1.doRun(DownsampleShardPersistentTaskExecutor.java:87) ~[?:?]
        at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26) ~[elasticsearch-8.11.0-SNAPSHOT.jar:?]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
        at java.lang.Thread.run(Thread.java:1623) ~[?:?]
```
x-pack/plugin/downsample/src/main/java/org/elasticsearch/xpack/downsample/DownsampleShardTaskParams.java
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
public record DownsampleShardTaskParams(
    DownsampleConfig downsampleConfig,
    String downsampleIndex,
    long indexStartTimeMillis,
    long indexEndTimeMillis,
    ShardId shardId,
    String[] metrics,
    String[] labels
) implements PersistentTaskParams {
    public static final String NAME = DownsampleShardTask.TASK_NAME;
    private static final ParseField DOWNSAMPLE_CONFIG = new ParseField("downsample_config");
    private static final ParseField DOWNSAMPLE_INDEX = new ParseField("rollup_index");
    private static final ParseField INDEX_START_TIME_MILLIS = new ParseField("index_start_time_millis");
    private static final ParseField INDEX_END_TIME_MILLIS = new ParseField("index_end_time_millis");
    private static final ParseField SHARD_ID = new ParseField("shard_id");
    private static final ParseField METRICS = new ParseField("metrics");
    private static final ParseField LABELS = new ParseField("labels");
    public static final ObjectParser<DownsampleShardTaskParams.Builder, Void> PARSER = new ObjectParser<>(NAME);
    static {
        PARSER.declareObject(
            DownsampleShardTaskParams.Builder::downsampleConfig,
            (p, c) -> DownsampleConfig.fromXContent(p),
            DOWNSAMPLE_CONFIG
        );
        PARSER.declareString(DownsampleShardTaskParams.Builder::downsampleIndex, DOWNSAMPLE_INDEX);
        PARSER.declareLong(DownsampleShardTaskParams.Builder::indexStartTimeMillis, INDEX_START_TIME_MILLIS);
        PARSER.declareLong(DownsampleShardTaskParams.Builder::indexEndTimeMillis, INDEX_END_TIME_MILLIS);