Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
LOG_INFO(log, "Setting max_server_memory_usage was set to {}"
                    " ({} available * {:.2f} max_server_memory_usage_to_ram_ratio)",
                    formatReadableSizeWithBinarySuffix(max_server_memory_usage),
                    formatReadableSizeWithBinarySuffix(memory_amount),
                    max_server_memory_usage_to_ram_ratio);
            }
            else if (max_server_memory_usage > default_max_server_memory_usage)
            {
                max_server_memory_usage = default_max_server_memory_usage;
                LOG_INFO(log, "Setting max_server_memory_usage was lowered to {}"
                    " because the system has low amount of memory. The amount was"
                    " calculated as {} available"
                    " * {:.2f} max_server_memory_usage_to_ram_ratio",
                    formatReadableSizeWithBinarySuffix(max_server_memory_usage),
                    formatReadableSizeWithBinarySuffix(memory_amount),
                    max_server_memory_usage_to_ram_ratio);
            }
            total_memory_tracker.setHardLimit(max_server_memory_usage);
            total_memory_tracker.setDescription("(total)");
            total_memory_tracker.setMetric(CurrentMetrics::MemoryTracking);
            
            
            
            
            global_context->setClustersConfig(config);
            global_context->setMacros(std::make_unique<Macros>(*config, "macros", log));
            global_context->setExternalAuthenticatorsConfig(*config);
            global_context->setExternalModelsConfig(config);
            
            if (config->has("max_table_size_to_drop"))