When I queried `system.metrics` table, I found some negative values which hint to some potential internal overflows.

```
SELECT *
FROM system.metrics
FORMAT Vertical

...

Row 31:
───────
metric:      MemoryTrackingInBackgroundProcessingPool
value:       -580863171
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround merges, mutations and fetches). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 32:
───────
metric:      MemoryTrackingInBackgroundMoveProcessingPool
value:       0
description: Total amount of memory (bytes) allocated in background processing pool (that is dedicated for backround moves). Note that this value may include a drift when the memory was allocated in a context of background processing pool and freed in other context or vice-versa. This happens naturally due to caches for tables indexes and doesn't indicate memory leaks.

Row 33:
───────
metric:      MemoryTrackingInBackgroundSchedulePool
value:       -4461308831
description: Total amount of memory (bytes) allocated in background schedule pool (that is dedicated for bookkeeping tasks of Replicated tables).

...

56 rows in set. Elapsed: 0.003 sec.
```

Server version: 20.8.2.3.
{
    auto lock = getLock();
    client_info.current_user = name;
    client_info.current_address = address;
#if defined(ARCADIA_BUILD)
    
    client_info.current_password = password.value_or("");
#endif
    
    UUID new_user_id;
    if (password)
        new_user_id = getAccessControlManager().login(name, *password, address.host());
    else
    {
        
        
        new_user_id = getAccessControlManager().getIDOfLoggedUser(name);
    }
    auto new_access = getAccessControlManager().getContextAccess(
        new_user_id,  {},  true,
        settings, current_database, client_info);
    user_id = new_user_id;
    access = std::move(new_access);
    current_roles.clear();
    use_default_roles = true;
    setSettings(*access->getDefaultSettings());
}
void Context::setUser(const String & name, const String & password, const Poco::Net::SocketAddress & address)