[C++][Acero] Support for multi threaded input: SortedMergeNode

[X-Lemon-X]

Describe the enhancement requested

Support for multi threading inputs (batches incoming not in order if they were ordered) and Backpressure support with node SortedMergeNode, previously resolved by disabling multi threading when using them.
I also created a PR with all the changes for this.

Component(s)

C++

[github-actions]

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