tableam: Use in CREATE TABLE AS and CREATE MATERIALIZED VIEW.

tableam: Use in CREATE TABLE AS and CREATE MATERIALIZED VIEW.

Previously those directly performed a heap_insert(). Use
table_insert() instead.  The input slot of those routines is not of
the target relation - we could fix that by copying if necessary, but
that'd not be beneficial for performance. As those codepaths don't
access any AM specific tuple fields (say xmin/xmax), there's no need
to use an AM specific slot.

Author: Andres Freund
Reviewed-By: Haribabu Kommi
Discussion: https://postgr.es/m/20180703070645[email protected]