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/Downsample.java
new NamedXContentRegistry.Entry(
                PersistentTaskParams.class,
                new ParseField(DownsampleShardTaskParams.NAME),
                DownsampleShardTaskParams::fromXContent
            )
        );
    }
    @Override
    public List<NamedWriteableRegistry.Entry> getNamedWriteables() {
        return List.of(
            new NamedWriteableRegistry.Entry(
                PersistentTaskState.class,
                DownsampleShardPersistentTaskState.NAME,
                DownsampleShardPersistentTaskState::readFromStream
            ),
            new NamedWriteableRegistry.Entry(
                PersistentTaskParams.class,
                DownsampleShardTaskParams.NAME,
                DownsampleShardTaskParams::readFromStream
            )
        );
    }
    @Override
    public Collection<Object> createComponents(
        final Client client,
        final ClusterService clusterService,
        final ThreadPool threadPool,
        final ResourceWatcherService resourceWatcherService,
        final ScriptService scriptService,
        final NamedXContentRegistry xContentRegistry,