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();
    return shared->config ? *shared->config : Poco::Util::Application::instance().config();
}
AccessControlManager & Context::getAccessControlManager()
{
    return shared->access_control_manager;
}
const AccessControlManager & Context::getAccessControlManager() const
{
    return shared->access_control_manager;
}
void Context::setExternalAuthenticatorsConfig(const Poco::Util::AbstractConfiguration & config)
{
    auto lock = getLock();
    shared->access_control_manager.setExternalAuthenticatorsConfig(config);
}
void Context::setUsersConfig(const ConfigurationPtr & config)
{
    auto lock = getLock();
    shared->users_config = config;
    shared->access_control_manager.setUsersConfig(*shared->users_config);
}
ConfigurationPtr Context::getUsersConfig()
{
    auto lock = getLock();
    return shared->users_config;
}
void Context::setUserImpl(const String & name, const std::optional<String> & password, const Poco::Net::SocketAddress & address)