pgsql: Forbid numeric NaN in jsonpath

Forbid numeric NaN in jsonpath

SQL standard doesn't define numeric Inf or NaN values.  It appears even more
ridiculous to support then in jsonpath assuming JSON doesn't support these
values as well.  This commit forbids returning NaN from .double(), which was
previously allowed.  NaN can't be result of inner-jsonpath computation over
non-NaNs.  So, we can not expect NaN in the jsonpath output.

Reported-by: Tom Lane
Discussion: https://postgr.es/m/203949.1591879542%40sss.pgh.pa.us
Author: Alexander Korotkov
Reviewed-by: Tom Lane
Backpatch-through: 12

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f4ae676e3178124c2bc2b3a3530efe8f3cdbc442

Modified Files
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src/backend/utils/adt/jsonb_util.c           |  8 --------
src/backend/utils/adt/jsonpath_exec.c        | 15 ++++++++-------
src/test/regress/expected/jsonb_jsonpath.out | 12 ++----------
3 files changed, 10 insertions(+), 25 deletions(-)