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();
    if (!shared->replicated_merge_tree_settings)
    {
        const auto & config = getConfigRef();
        MergeTreeSettings mt_settings;
        mt_settings.loadFromConfig("merge_tree", config);
        mt_settings.loadFromConfig("replicated_merge_tree", config);
        shared->replicated_merge_tree_settings.emplace(mt_settings);
    }
    return *shared->replicated_merge_tree_settings;
}
const StorageS3Settings & Context::getStorageS3Settings() const
{
#if !defined(ARCADIA_BUILD)
    auto lock = getLock();
    if (!shared->storage_s3_settings)
    {
        const auto & config = getConfigRef();
        shared->storage_s3_settings.emplace().loadFromConfig("s3", config);
    }
    return *shared->storage_s3_settings;
#else
    throw Exception("S3 is unavailable in Arcadia", ErrorCodes::NOT_IMPLEMENTED);
#endif
}
void Context::checkCanBeDropped(const String & database, const String & table, const size_t & size, const size_t & max_size_to_drop) const