pgsql: SQL/JSON: Fix error-handling of some JsonBehavior expressions

SQL/JSON: Fix error-handling of some JsonBehavior expressions

To ensure that the errors of executing a JsonBehavior expression that
is coerced in the parser are caught instead of being thrown directly,
pass ErrorSaveContext to ExecInitExprRec() when initializing it.
Also, add a EEOP_JSONEXPR_COERCION_FINISH step to handle the errors
that are caught that way.

Discussion: https://postgr.es/m/CACJufxEo4sUjKCYtda0_qt9tazqqKPmF1cqhW9KBOUeJFqQd2g@mail.gmail.com
Backpatch-through: 17

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/63e6c5f4a2eeb22e0dd446a62c2b4b417d2b51f0

Modified Files
--------------
src/backend/executor/execExpr.c                  | 51 +++++++++++++++++++++++-
src/backend/executor/execExprInterp.c            |  6 +++
src/test/regress/expected/sqljson_jsontable.out  |  6 ++-
src/test/regress/expected/sqljson_queryfuncs.out |  6 ++-
4 files changed, 65 insertions(+), 4 deletions(-)