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?
{
#if defined(THREAD_SANITIZER) && defined(OS_LINUX)
    
    
    (void)syscall(SYS_exit_group, 0);
    __builtin_unreachable();
#else
    _exit(0);
#endif
}
int Server::main(const std::vector<std::string> & )
{
    Poco::Logger * log = &logger();
    UseSSL use_ssl;
    MainThreadStatus::getInstance();
    registerFunctions();
    registerAggregateFunctions();
    registerTableFunctions();
    registerStorages();
    registerDictionaries();