pgsql: Avoid listing the same ResultRelInfo in more than one EStatelis

Avoid listing the same ResultRelInfo in more than one EState list.

Doing so causes EXPLAIN ANALYZE to show trigger statistics multiple
times.  Commit 2f178441044be430f6b4d626e4dae68a9a6f6cec seems to
be to blame for this.

Amit Langote, revieed by Amit Khandekar, Etsuro Fujita, and me.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/e44dd84325c277fd031b9ef486c51a0946c7d3a0

Modified Files
--------------
src/backend/commands/explain.c       | 11 +++++++----
src/backend/executor/execMain.c      |  7 +++++--
src/backend/executor/execPartition.c | 12 +++++++++---
src/backend/executor/execUtils.c     |  2 +-
src/include/nodes/execnodes.h        |  7 +++++--
5 files changed, 27 insertions(+), 12 deletions(-)