pgsql: Move FOR PORTION OF volatile check into planner

Move FOR PORTION OF volatile check into planner

This needs to be wary of the function volatility changing after we
check it. We cannot enforce this when checking at parse time, so move
it later, into the planner.

Author: Paul A. Jungwirth <pj(at)illuminatedcomputing(dot)com>
Reported-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: jian he <jian(dot)universality(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/flat/CA%2BrenyUte0_UJsJiDJQi82oaBsMJn%3Dcct0Wn%3DvOqXtuDn%3DYYJA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a272a58b94249879c3f7e170a5ebfaeec940d411

Modified Files
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src/backend/optimizer/plan/planner.c | 12 ++++++++++++
src/backend/parser/analyze.c | 3 ---
2 files changed, 12 insertions(+), 3 deletions(-)