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
final long availableBytesPerSec = Math.min(readBytesPerSec, writeBytesPerSec);
        assert nodeBandwidthSettingsExist == (availableBytesPerSec != 0L);
        long maxBytesPerSec;
        if (availableBytesPerSec == 0L                                      
            || INDICES_RECOVERY_MAX_BYTES_PER_SEC_SETTING.exists(settings)  
            || DiscoveryNode.canContainData(settings) == false) {           
            maxBytesPerSec = defaultBytesPerSec;
        } else {
            maxBytesPerSec = Math.max(defaultBytesPerSec, availableBytesPerSec);
        }
        final long maxAllowedBytesPerSec = Math.round(
            Math.max(
                Math.min(
                    Math.min(availableDiskReadBandwidth.getBytes(), availableDiskWriteBandwidth.getBytes()),
                    networkBandwidthBytesPerSec
                ),
                0L
            ) * NODE_BANDWIDTH_RECOVERY_OPERATOR_FACTOR_MAX_OVERCOMMIT_SETTING.get(settings)
        );
        ByteSizeValue finalMaxBytesPerSec;
        if (maxAllowedBytesPerSec > 0L) {
            if (maxBytesPerSec > 0L) {
                finalMaxBytesPerSec = ByteSizeValue.ofBytes(Math.min(maxBytesPerSec, maxAllowedBytesPerSec));
            } else {
                finalMaxBytesPerSec = ByteSizeValue.ofBytes(maxAllowedBytesPerSec);
            }
        } else {
            finalMaxBytesPerSec = ByteSizeValue.ofBytes(maxBytesPerSec);
        }
        logger.info(