Refactor reduction logic for fixed-point types

[davidwendt]

Description

Reworks some internal source specific to fixed-point types using cudf::reduce by removing the duplicated code logic. This was found while working on #12573 and #10432. Since the fix is requires no dependencies, this separate PR is used to minimize code review churn. This should help with code consistency with the fixed-point-specific logic when added to segmented-reduction.
No function has changed so all existing gtests are adequate.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (branch-23.04@97a746f). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@               Coverage Diff               @@
##             branch-23.04   #12652   +/-   ##
===============================================
  Coverage                ?   85.81%           
===============================================
  Files                   ?      158           
  Lines                   ?    25153           
  Branches                ?        0           
===============================================
  Hits                    ?    21586           
  Misses                  ?     3567           
  Partials                ?        0           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[bdice]

LGTM.

[davidwendt]

/merge