Backend-specific contents in common code spaces

[zhztheplayer]

@apache/gluten-committers

We now have some code that is for VL / CH backend specifically, but placed in common code module. A typical one we are all aware of is backends' CPP code. Velox's is under cpp while CH's is under cpp-ch. I am looking for a good timing to move them to their own modules (backends-velox / backends-clickhouse).

If you have some thoughts on this, please comment or reply to this email thread. Thanks.

[zhztheplayer]

Oops, sorry. I feel I notified the root Apache group by accident. Please ignore the notification.