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
INDICES_RECOVERY_MAX_BYTES_PER_SEC_SETTING,
                    NODE_BANDWIDTH_RECOVERY_FACTOR_READ_SETTING,
                    NODE_BANDWIDTH_RECOVERY_FACTOR_WRITE_SETTING,
                    NODE_BANDWIDTH_RECOVERY_OPERATOR_FACTOR_SETTING,
                    NODE_BANDWIDTH_RECOVERY_OPERATOR_FACTOR_READ_SETTING,
                    NODE_BANDWIDTH_RECOVERY_OPERATOR_FACTOR_WRITE_SETTING,
                    NODE_BANDWIDTH_RECOVERY_OPERATOR_FACTOR_MAX_OVERCOMMIT_SETTING,
                    
                    NODE_BANDWIDTH_RECOVERY_DISK_WRITE_SETTING,
                    NODE_BANDWIDTH_RECOVERY_DISK_READ_SETTING,
                    NODE_BANDWIDTH_RECOVERY_NETWORK_SETTING,
                    NODE_ROLES_SETTING
                )
            );
        }
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_MAX_CONCURRENT_FILE_CHUNKS_SETTING, this::setMaxConcurrentFileChunks);
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_MAX_CONCURRENT_OPERATIONS_SETTING, this::setMaxConcurrentOperations);
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_RETRY_DELAY_STATE_SYNC_SETTING, this::setRetryDelayStateSync);
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_RETRY_DELAY_NETWORK_SETTING, this::setRetryDelayNetwork);
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_INTERNAL_ACTION_TIMEOUT_SETTING, this::setInternalActionTimeout);
        clusterSettings.addSettingsUpdateConsumer(
            INDICES_RECOVERY_INTERNAL_LONG_ACTION_TIMEOUT_SETTING,
            this::setInternalActionLongTimeout
        );
        clusterSettings.addSettingsUpdateConsumer(
            INDICES_RECOVERY_INTERNAL_ACTION_RETRY_TIMEOUT_SETTING,
            this::setInternalActionRetryTimeout
        );
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_ACTIVITY_TIMEOUT_SETTING, this::setActivityTimeout);
        clusterSettings.addSettingsUpdateConsumer(INDICES_RECOVERY_USE_SNAPSHOTS_SETTING, this::setUseSnapshotsDuringRecovery);