pgsql: Post review fixes for test_json_parser test module

Post review fixes for test_json_parser test module

. Add missing copytight notices
. improve code coverage
. put work files in a temp directory in the standard location
. improve error checking in C code
. indent perl files with perltidy
. add some comments

per comments from Michael Paquier

Discussion: https://postgr.es/m/ZiC3-cdFys4-6xSk@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ba3e6e2bca97df14920375b0a1ebf4eab95b78b5

Modified Files
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.../t/001_test_json_parser_incremental.pl          | 15 +++-
src/test/modules/test_json_parser/t/002_inline.pl  | 93 ++++++++++++++++------
.../test_json_parser/t/003_test_semantic.pl        | 15 +++-
.../test_json_parser/t/004_test_parser_perf.pl     | 18 +++--
.../test_json_parser_incremental.c                 | 25 ++++--
.../test_json_parser/test_json_parser_perf.c       | 13 ++-
src/test/modules/test_json_parser/tiny.json        |  1 +
src/test/modules/test_json_parser/tiny.out         |  1 +
8 files changed, 133 insertions(+), 48 deletions(-)