pgsql: Stabilize btree_gist test against on-access VM setting

Stabilize btree_gist test against on-access VM setting

The btree_gist enum test expects a bitmap heap scan. Since b46e1e54d07
enabled setting the VM during on-access pruning and 378a21618 set
pd_prune_xid on INSERT, scans of enumtmp may set pages all-visible.
If autovacuum or autoanalyze then updates pg_class.relallvisible, the
planner could choose an index-only scan instead.

Make the enumtmp a temp table to exclude it from autovacuum/autoanalyze.

Reported-by: Alexander Lakhin <exclusion(at)gmail(dot)com>
Author: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Discussion: https://postgr.es/m/46733d68-aec0-4d09-8120-4c66b87047a4%40gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/62407d26b7c9e619ed696fced88fdacc5d1ae522

Modified Files
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contrib/btree_gist/expected/enum.out | 2 +-
contrib/btree_gist/sql/enum.sql | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)