pgsql: Second attempt at organizing jsonpath operators and methods

Second attempt at organizing jsonpath operators and methods

Second attempt at 283a95da923.  Since we can't reorder the enum values
of JsonPathItemType, instead reorder the switch cases where they are
used to generally follow the order of the enum values, for better
maintainability.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/59fd390d5e8a7e169ff8f095882e32e189f3c5bd

Modified Files
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src/backend/utils/adt/jsonpath.c      | 250 ++++++++++++-------------
src/backend/utils/adt/jsonpath_exec.c | 332 +++++++++++++++++-----------------
src/include/utils/jsonpath.h          |   7 +
3 files changed, 298 insertions(+), 291 deletions(-)