This adds one metric per log stream and one metric per log writer (path based)
to track the number of writes on a stream level as well as on a writer level.
$ curl -sSf localhost:8181/metrics | grep Conn
zeek_log_writer_writes_total{endpoint="",filter-name="default",module="HTTP",path="http",stream="HTTP::LOG",writer="Log::WRITER_SQLITE"} 1 1677497572770
zeek_log_stream_writes_total{endpoint="",module="HTTP",stream="HTTP::LOG"} 1 1677497572770
The initial version of this change also included metrics around log
write vetoes, but given no log policies exist in the default configuration
and they are mostly interesting for a few streams/writers only, skip this
for now. These can always be added by the script writer, too.
The difference between the stream level writes and concrete writers can
be used to deduce the number of vetoes (or errors) as a starting point.
