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?
#include <Common/DNSResolver.h>
#include <Common/CurrentMetrics.h>
#include <Common/Macros.h>
#include <Common/ShellCommand.h>
#include <Common/StringUtils/StringUtils.h>
#include <Common/ZooKeeper/ZooKeeper.h>
#include <Common/ZooKeeper/ZooKeeperNodeCache.h>
#include <common/getFQDNOrHostName.h>
#include <Common/getMultipleKeysFromConfig.h>
#include <Common/getNumberOfPhysicalCPUCores.h>
#include <Common/getExecutablePath.h>
#include <Common/ThreadProfileEvents.h>
#include <Common/ThreadStatus.h>
#include <Common/getMappedArea.h>
#include <Common/remapExecutable.h>
#include <Common/TLDListsHolder.h>
#include <IO/HTTPCommon.h>
#include <IO/ReadHelpers.h>
#include <IO/UseSSL.h>
#include <Interpreters/AsynchronousMetrics.h>
#include <Interpreters/DDLWorker.h>
#include <Interpreters/ExternalDictionariesLoader.h>
#include <Interpreters/ExternalModelsLoader.h>
#include <Interpreters/ProcessList.h>
#include <Interpreters/loadMetadata.h>
#include <Interpreters/DatabaseCatalog.h>
#include <Interpreters/DNSCacheUpdater.h>
#include <Interpreters/ExternalLoaderXMLConfigRepository.h>
#include <Interpreters/InterserverCredentials.h>
#include <Interpreters/JIT/CompiledExpressionCache.h>