pgsql: Fix string comparison in jsonpath

Fix string comparison in jsonpath

Take into account pg_server_to_any() may return input string "as is".

Reported-by: Andrew Dunstan, Thomas Munro
Discussion: https://postgr.es/m/0ed83a33-d900-466a-880a-70ef456c721f%402ndQuadrant.com
Author: Alexander Korotkov, Thomas Munro
Backpatch-through: 12

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/de0dc0b758ed7452ceee756d9d620c4393b3cb53

Modified Files
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src/backend/utils/adt/jsonpath_exec.c | 37 +++++++++++++++++++++++++++--------
1 file changed, 29 insertions(+), 8 deletions(-)