pgsql: Revert "Rewrite some RI code to avoid using SPI"

Revert "Rewrite some RI code to avoid using SPI"

This reverts commit 99392cdd78b788295e52b9f4942fa11992fd5ba9.
We'd rather rewrite ri_triggers.c as a whole rather than piecemeal.

Discussion: https://postgr.es/m/E1ncXX2-000mFt-Pe@gemulon.postgresql.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a90641eac24dfc8889122d88eb7f482cd3db8b39

Modified Files
--------------
src/backend/executor/execPartition.c        | 174 +--------
src/backend/executor/nodeLockRows.c         | 161 ++++----
src/backend/utils/adt/ri_triggers.c         | 564 ++++++++++++----------------
src/include/executor/execPartition.h        |   6 -
src/include/executor/executor.h             |   8 -
src/test/isolation/expected/fk-snapshot.out |   4 +-
src/test/isolation/specs/fk-snapshot.spec   |   5 +-
7 files changed, 317 insertions(+), 605 deletions(-)