We limit the number of concurrent blob downloads per node and per recovery, but if a user configures too many concurrent recoveries they may run out of per-node download permits which yields the following message:

> Unable to acquire permit to use snapshot files during recovery, this recovery will recover index files from the source node. Ensure snapshot files can be used during recovery by setting [indices.recovery.max_concurrent_snapshot_file_downloads] to be no greater than [25]

The `[25]` here is wrong, the 25 permits are shared across all inbound recoveries so we should divide the suggested value by `cluster.routing.allocation.node_concurrent_incoming_recoveries`. In extreme cases the user may have configured so many concurrent recoveries that the only reasonable limit is zero, and in that case we should suggest setting `indices.recovery.use_snapshots: false` instead.


server/src/main/java/org/elasticsearch/indices/recovery/RecoverySettings.java
);
    public static final Setting<Integer> INDICES_RECOVERY_MAX_CONCURRENT_SNAPSHOT_FILE_DOWNLOADS = Setting.intSetting(
        "indices.recovery.max_concurrent_snapshot_file_downloads",
        5,
        1,
        20,
        Property.Dynamic,
        Property.NodeScope
    );
    public static final Setting<Integer> INDICES_RECOVERY_MAX_CONCURRENT_SNAPSHOT_FILE_DOWNLOADS_PER_NODE = new Setting<>(
        "indices.recovery.max_concurrent_snapshot_file_downloads_per_node",
        "25",
        (s) -> parseInt(s, 1, 25, "indices.recovery.max_concurrent_snapshot_file_downloads_per_node", false),
        new Setting.Validator<>() {
            private final Collection<Setting<?>> dependencies = Collections.singletonList(
                INDICES_RECOVERY_MAX_CONCURRENT_SNAPSHOT_FILE_DOWNLOADS
            );
            @Override
            public void validate(Integer value) {
                
            }
            @Override
            public void validate(Integer maxConcurrentSnapshotFileDownloadsPerNode, Map<Setting<?>, Object> settings) {
                int maxConcurrentSnapshotFileDownloads = (int) settings.get(INDICES_RECOVERY_MAX_CONCURRENT_SNAPSHOT_FILE_DOWNLOADS);
                if (maxConcurrentSnapshotFileDownloadsPerNode < maxConcurrentSnapshotFileDownloads) {
                    throw new IllegalArgumentException(
                        String.format(
                            Locale.ROOT,
                            "[%s]=%d is less than [%s]=%d",
                            INDICES_RECOVERY_MAX_CONCURRENT_SNAPSHOT_FILE_DOWNLOADS_PER_NODE.getKey(),