pgsql: Add permission check for MERGE/SPLIT partition operations

Add permission check for MERGE/SPLIT partition operations

Currently, we check only owner permission for the parent table before
MERGE/SPLIT partition operations. This leads to a security hole when users
can get access to the data of partitions without permission. This commit
fixes this problem by requiring owner permission on all the partitions
involved.

Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/0520c72e-8d97-245e-53f9-173beca2ab2e%40gmail.com
Author: Dmitry Koval, Alexander Korotkov

Branch
------
master

Details
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https://git.postgresql.org/pg/commitdiff/3ca43dbbb67fbfb96dec8de2e268b96790555148

Modified Files
--------------
src/backend/parser/parse_utilcmd.c | 5 ++++
src/test/regress/expected/partition_merge.out | 29 +++++++++++++++++++++++
src/test/regress/expected/partition_split.out | 29 +++++++++++++++++++++++
src/test/regress/sql/partition_merge.sql | 33 +++++++++++++++++++++++++++
src/test/regress/sql/partition_split.sql | 33 +++++++++++++++++++++++++++
5 files changed, 129 insertions(+)