feature: Use amflags to support Column-oriented scanning of custom ta…

[gongxun0928]

fix #ISSUE_Number

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Change logs

For custom tableam, maybe it support column-oriented scanning, the postgres planner can no longer use whether am_handler is aocs table_am to decide whether only to add the columns required by the operator to the targetlist.

If table am supports column-oriented scanning, the flags returned by set_flags set the SCAN_SUPPORT_COLUMN_ORIENTED_SCAN bit.

Why are the changes needed?

I hope that custom column storage can also scan only necessary columns, instead of only aocs table am support

Does this PR introduce any user-facing change?

no

How was this patch tested?

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[gfphoenix78]

LGTM