This metric tracks an approximate amounts of bytes processed when parsing the ingested logs.
The metric is exposed individually per every supported data ingestion protocol. The protocol name
is exposed via "type" label in order to be consistent with vl_rows_ingested_total metric.
Thanks to @tenmozes for the initial idea and implementation at https://github.com/VictoriaMetrics/VictoriaMetrics/pull/7682
While at it, remove the unneeded "format" label from vl_rows_ingested_total metric.
The "type" label must be enough for encoding the data ingestion format.
This msy be useful when ingesting logs from different sources, which store the log message in different fields.
For example, `_msg_field=message,event.data,some_field` will get log message from the first non-empty field:
`message`, `event.data` and `some_field`.
Empty fields are treated as non-existing fields by VictoriaLogs data model.
So there is no sense in returning empty fields in query results, since they may mislead and confuse users.
