pgsql: Support TRUNCATE triggers on foreign tables.

Support TRUNCATE triggers on foreign tables.

Now some foreign data wrappers support TRUNCATE command.
So it's useful to support TRUNCATE triggers on foreign tables for
audit logging or for preventing undesired truncation.

Author: Yugo Nagata
Reviewed-by: Fujii Masao, Ian Lawrence Barwick
Discussion: https://postgr.es/m/20220630193848.5b02e0d6076b86617a915682@sraoss.co.jp

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3b00a944a9b3847fb02dae7c9ea62fe0b211b396

Modified Files
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contrib/postgres_fdw/expected/postgres_fdw.out | 9 ++++++---
contrib/postgres_fdw/sql/postgres_fdw.sql      | 5 +++--
doc/src/sgml/ref/create_trigger.sgml           | 4 ++--
src/backend/commands/trigger.c                 | 7 -------
4 files changed, 11 insertions(+), 14 deletions(-)