ARROW-17932: [C++] Implement streaming RecordBatchReader for JSON (#14355)

See: [ARROW-17932](https://issues.apache.org/jira/browse/ARROW-17932).

Adds a `json::StreamingReader` class (modeled after `csv::StreamingReader`) with an async-reentrant interface and support for parallel block decoding.

Some parts of the existing `TableReader` implementation have been refactored to utilize the new facilities.

Lead-authored-by: benibus <bpharks@gmx.com>
Co-authored-by: Ben Harkins <60872452+benibus@users.noreply.github.com>
Co-authored-by: Will Jones <willjones127@gmail.com>
Co-authored-by: Antoine Pitrou <pitrou@free.fr>
Signed-off-by: Antoine Pitrou <antoine@python.org>

Author: 3 people