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
mockAppender.assertAllExpectationsMatched();
        } finally {
            Loggers.removeAppender(logger, mockAppender);
            mockAppender.stop();
        }
    }
    private static ByteSizeValue randomNonZeroByteSizeValue() {
        return ByteSizeValue.ofBytes(randomLongBetween(1L, Long.MAX_VALUE >> 16));
    }
    private static Set<String> randomDataNodeRoles() {
        final Set<String> roles = new HashSet<>(randomSubsetOf(randomIntBetween(1, 4), "data", "data_hot", "data_warm", "data_content"));
        roles.addAll(randomSubsetOf(Set.of("data_cold", "data_frozen")));
        if (randomBoolean()) {
            roles.addAll(
                randomSubsetOf(
                    DiscoveryNodeRole.roles()
                        .stream()
                        .filter(role -> role != DiscoveryNodeRole.VOTING_ONLY_NODE_ROLE)
                        .filter(role -> role.canContainData() == false)
                        .map(DiscoveryNodeRole::roleName)
                        .collect(Collectors.toSet())
                )
            );
        }
        return roles;
    }
    private static NodeRecoverySettings nodeRecoverySettings() {
        return new NodeRecoverySettings();
    }
    private static class NodeRecoverySettings {