arrow

ARROW-18184: [C++] Improve JSON parser benchmarks (#14552)

See: [ARROW-18184](https://issues.apache.org/jira/browse/ARROW-18184).

For context, this is based on [pull/14100](https://github.com/apache/arrow/pull/14100).

This enhances the capabilities of the existing random JSON generators and adds benchmark coverage for ordered/unordered fields, missing fields, and inferred schemas over a range of field counts.

Lead-authored-by: benibus <bpharks@gmx.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Co-authored-by: Ben Harkins <60872452+benibus@users.noreply.github.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Signed-off-by: Antoine Pitrou <antoine@python.org>