pgsql: Get rid of jsonpath_gram.h and jsonpath_scanner.h

Get rid of jsonpath_gram.h and jsonpath_scanner.h

Jsonpath grammar and scanner are both quite small.  It doesn't worth complexity
to compile them separately.  This commit makes grammar and scanner be compiled
at once.  Therefore, jsonpath_gram.h and jsonpath_gram.h are no longer needed.
This commit also does some reorganization of code in jsonpath_gram.y.

Discussion: https://postgr.es/m/d47b2023-3ecb-5f04-d253-d557547cf74f%402ndQuadrant.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/550b9d26f80fa3048f2d5883f0779ed29465960a

Modified Files
--------------
src/backend/Makefile                  |  13 +-
src/backend/utils/adt/.gitignore      |   1 -
src/backend/utils/adt/Makefile        |  21 +-
src/backend/utils/adt/jsonpath_gram.y | 485 ++++++++++++++++++----------------
src/backend/utils/adt/jsonpath_scan.l |   4 +-
src/include/Makefile                  |   4 +-
src/include/utils/.gitignore          |   1 -
src/include/utils/jsonpath_scanner.h  |  32 ---
src/tools/msvc/Solution.pm            |  18 --
9 files changed, 268 insertions(+), 311 deletions(-)