REF: avoid use of to_perioddelta
tslibs is nominally self-contained, but several offsets methods still rely on DatetimeArray/PeriodArray behavior.  This is the first of several steps whittling that away.
sure can we completely remove to_perioddelta? > sure can we completely remove to_perioddelta?

hopefully, but the remaining usages aren't as striaghtforward. xref #34555 moving in that direction.