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ARROW-11772: [C++] Provide reentrant IPC file reader

This provides an async-reentrant generator of record batches from an IPC file reader, intended to support Datasets once it becomes async itself.

IPC messages are read on an IO thread pool, then decoded on the CPU thread pool. All dictionaries must be read at the start, then record batches can be read independently.

Closes #9656 from lidavidm/arrow-11772

Lead-authored-by: David Li <li.davidm96@gmail.com>
Co-authored-by: Antoine Pitrou <antoine@python.org>
Signed-off-by: David Li <li.davidm96@gmail.com>