* use the new packed reader and writer api to be compatible with current
etcd meta
* For the new packed writer API: column groups and paths are explicitly
defined by users and won't split column groups by memory in storage v2.
Packed writer follows the user-defined column groups to split arrow
record and write into the corresponding file path.
* For the new packed reader API: read paths are explicitly defined by
users.
related: #39173
Signed-off-by: shaoting-huang <shaoting.huang@zilliz.com>
sthuang