[fix] Corrected pulsar_storage_size metric to not multiply offloaded storage by the write quorum

[dlg99]

Motivation

I think pulsar_storage_size is partially double-counted. Currently
pulsar_storage_size = pulsar_storage_logical_size * number of replicas

Number of replicas is the same as the bookie write quorum.
pulsar_logical_size doesn't account for the replication, it is sum of customer bytes no matter where they stored at.
and it looks like pulsar_storage_logical_size (calculated here initially) DOES include pulsar_storage_offloaded_size (calculated here).
But the offloaded ledgers (e.g. S3) do not create multiple replicas.

I think the metric should be calculated as:
pulsar_storage_size = pulsar_storage_offloaded_size + (pulsar_storage_logical_size - pulsar_storage_offloaded_size) * number of replicas

Modifications

adjusted calculations of pulsar_storage_size

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