pgsql: Make ALTER TRIGGER RENAME consistent for partitioned tables

Make ALTER TRIGGER RENAME consistent for partitioned tables

Renaming triggers on partitioned tables had two problems: first,
it did not recurse to renaming the triggers on the partitions; and
second, it failed to prohibit renaming clone triggers. Having triggers
with different names in partitions is pointless, and furthermore pg_dump
would not preserve names for partitions anyway.

Not backpatched -- making the ALTER TRIGGER throw an error in stable
versions might cause problems for existing scripts.

Co-authored-by: Arne Roland <A(dot)Roland(at)index(dot)de>
Co-authored-by: Álvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Reviewed-by: Zhihong Yu <zyu(at)yugabyte(dot)com>
Discussion: https://postgr.es/m/d0fd7040c2fb4de1a111b9d9ccc456b8@index.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/80ba4bb383538a2ee846fece6a7b8da9518b6866

Modified Files
--------------
doc/src/sgml/ref/alter_trigger.sgml | 15 ++-
src/backend/commands/trigger.c | 214 ++++++++++++++++++++++++++-------
src/test/regress/expected/triggers.out | 76 ++++++++++++
src/test/regress/sql/triggers.sql | 47 ++++++++
4 files changed, 307 insertions(+), 45 deletions(-)