metric DiskDataBytes can be incorrect due to inactive parts & hardlinks

[filimonov]

After mutation (especially noop mutation) the whole dataset becomes inactive, and hardlink-copy of that becomes active.

We count both active & inactive in one single metric

clickhouse-operator/pkg/apis/metrics/clickhouse_metrics_fetcher.go

Line 96 in b0dc549

toString(sum(bytes_on_disk)) AS metric_DiskDataBytes,

clickhouse-operator/pkg/apis/metrics/prometheus_writer.go

Line 139 in b0dc549

diskDataBytes += m[0]

and that may look like the table consumes twice the disk space.

I would count activeparts disk space and inactive parts disk space separately.

Also that metric does not account temp files & detached parts and non-mergetree data etc (so the name is not the best).