[C++] Fix use of non-const references in temporal kernels

[asfimport]

See final comments in #11075

Reporter: David Li / @lidavidm
Assignee: David Li / @lidavidm

Related issues:

• [C++] iso_calendar may be uninitialized (duplicates)

_{Note: This issue was originally created as ARROW-13960. Please see the migration documentation for further details.}