pgsql: Fix memory leak in IndexScan node with reordering

Fix memory leak in IndexScan node with reordering

Fix ExecReScanIndexScan() to free the referenced tuples while emptying the
priority queue.  Backpatch to all supported versions.

Discussion: https://postgr.es/m/CAHqSB9gECMENBQmpbv5rvmT3HTaORmMK3Ukg73DsX5H7EJV7jw%40mail.gmail.com
Author: Aliaksandr Kalenik
Reviewed-by: Tom Lane, Alexander Korotkov
Backpatch-through: 10

Branch
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REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2e9033a548041151e32f070cecc9dee154e8fb98

Modified Files
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src/backend/executor/nodeIndexscan.c       |  6 +++++-
src/test/regress/expected/create_index.out | 27 +++++++++++++++++++++++++++
src/test/regress/sql/create_index.sql      |  4 ++++
3 files changed, 36 insertions(+), 1 deletion(-)