[C++][Acero] Add support for any scalar type in pivot longer

[gitmodimo]

Describe the enhancement requested

Current implementation does not support features different than string. It looks easy enough to support any Scalar type.

Component(s)

C++

[github-actions]

This issue has been marked as stale because it has had no activity in the past 365 days. Please remove the stale label or comment below, or this issue will be closed in 14 days. If this improvement is still desired but has no current owner, please add the 'Status: needs champion' label.

[pitrou]

Issue resolved by pull request 47391
#47391