pgsql: Support for deparsing of ArrayCoerceExpr node in contrib/postgre

Support for deparsing of ArrayCoerceExpr node in contrib/postgres_fdw

When using a prepared statement to select data from a PostgreSQL foreign
table (postgres_fdw) with the "field = ANY($1)" expression, the operation
is not pushed down when an implicit type case is applied, and a generic plan
is used. This commit resolves the issue by supporting the push-down of
ArrayCoerceExpr, which is used in this case. The support is quite
straightforward and similar to other nods, such as RelabelType.

Discussion: https://postgr.es/m/4f0cea802476d23c6e799512ffd17aff%40postgrespro.ru
Author: Alexander Pyhalov <a(dot)pyhalov(at)postgrespro(dot)ru>
Reviewed-by: Maxim Orlov <orlovmg(at)gmail(dot)com>
Reviewed-by: Alexander Korotkov <aekorotkov(at)gmail(dot)com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/62c3b4cd9ddc6d3066e3f6e43b68fd00c620d9ad

Modified Files
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contrib/postgres_fdw/deparse.c | 50 ++++++++++++++++++++++++++
contrib/postgres_fdw/expected/postgres_fdw.out | 21 +++++++++++
contrib/postgres_fdw/sql/postgres_fdw.sql | 9 +++++
3 files changed, 80 insertions(+)