chunk compression type is hardcoded to passthrough for metric columns

There doesn't seem to be a way to use LZ4 compression for metric column.

https://github.com/apache/pinot/blob/f2f8e38f9424bcacf3946197c9afcd50ef1d58fa/pinot-segment-local/src/main/java/org/apache/pinot/segment/local/realtime/converter/RealtimeSegmentConverter.java#L100

Start in pinot-segment-local/src/main/java/org/apache/pinot/segment/local/realtime/converter/RealtimeSegmentConverter.java at the linked line, and trace how the compression type is chosen for metric columns. Confirm the existing configuration or conversion path for metric-column compression; done means LZ4 can be selected instead of passthrough.

Written by the indexing model from the issue text.