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ARROW-11070: [C++][Compute] Implement power kernel

This is to resolve [ARROW-11070](https://issues.apache.org/jira/projects/ARROW/issues/ARROW-11070).

Closes #9841 from rok/ARROW-11070

Lead-authored-by: Rok <rok@mihevc.org>
Co-authored-by: Yibo Cai <yibo.cai@arm.com>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>