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/test/java/org/elasticsearch/indices/recovery/RecoverySettingsTests.java
}
            return this;
        }
        NodeRecoverySettings withNetworkBandwidth(ByteSizeValue networkBandwidth) {
            this.networkBandwidth = networkBandwidth;
            return this;
        }
        NodeRecoverySettings withDiskReadBandwidth(ByteSizeValue diskReadBandwidth) {
            this.diskReadBandwidth = diskReadBandwidth;
            return this;
        }
        NodeRecoverySettings withDiskWriteBandwidth(ByteSizeValue diskWriteBandwidth) {
            this.diskWriteBandwidth = diskWriteBandwidth;
            return this;
        }
        NodeRecoverySettings withRandomBandwidths() {
            if (randomBoolean()) {
                withNetworkBandwidth(randomNonZeroByteSizeValue());
                withDiskReadBandwidth(randomNonZeroByteSizeValue());
                withDiskWriteBandwidth(randomNonZeroByteSizeValue());
            }
            return this;
        }
        NodeRecoverySettings withOperatorDefaultFactor(Double factor) {
            this.operatorDefaultFactor = factor;
            return this;
        }
        NodeRecoverySettings withMaxOvercommitFactor(Double factor) {
            this.maxOvercommitFactor = factor;
            return this;