feat: improve sink metrics

[fuyufjh]

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What's changed and what's your intention?

Some misc. follow-ups of #18730

• Refactor connector_sink_rows_received: should have actor_id as label
• Refactor LogWriterMetrics: remove the connector label for log writer metrics
• Removed the "CDC Connector" section of Grafana.
  • Removed source_rows_received because it was designed for Java CDC connector and should be replaced by source throughput now.
  • Moved "Remote Sink (Java) Throughput" to Sink section.

Checklist

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Release note

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[chenzl25]

LGTM