Related to #43522
Currently, passing partial schema to storage v2 packed reader may
trigger SEGV during clustering compaction unit test.
This patch implement `NeededFields` differently in each `RecordReader`
imlementation. For now, v2 will implemented as no-op. This will be
supported after packed reader support this API.
---------
Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>