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?
double cache_size_to_ram_max_ratio = config().getDouble("cache_size_to_ram_max_ratio", 0.5);
    size_t max_cache_size = memory_amount * cache_size_to_ram_max_ratio;
    
    size_t uncompressed_cache_size = config().getUInt64("uncompressed_cache_size", 0);
    if (uncompressed_cache_size > max_cache_size)
    {
        uncompressed_cache_size = max_cache_size;
        LOG_INFO(log, "Uncompressed cache size was lowered to {} because the system has low amount of memory",
            formatReadableSizeWithBinarySuffix(uncompressed_cache_size));
    }
    global_context->setUncompressedCache(uncompressed_cache_size);
    
    global_context->setDefaultProfiles(config());
    const Settings & settings = global_context->getSettingsRef();
    
    size_t mark_cache_size = config().getUInt64("mark_cache_size");
    if (!mark_cache_size)
        LOG_ERROR(log, "Too low mark cache size will lead to severe performance degradation.");
    if (mark_cache_size > max_cache_size)
    {
        mark_cache_size = max_cache_size;
        LOG_INFO(log, "Mark cache size was lowered to {} because the system has low amount of memory",
            formatReadableSizeWithBinarySuffix(mark_cache_size));
    }
    global_context->setMarkCache(mark_cache_size);
    
    size_t mmap_cache_size = config().getUInt64("mmap_cache_size", 1000);   
    if (mmap_cache_size)
        global_context->setMMappedFileCache(mmap_cache_size);
#if USE_EMBEDDED_COMPILER