Webform Test logic for date list is broken

Problem/Motivation

The logic that determines the contents of a date list when doing a form test is different than that of the live form and is not correct.

Steps to reproduce

Given a date list field that specifies Years as the date part and 0:+4 as the range, the list should (and does when Viewing) contain:
2025
2026
2027
2028
2029

but the Test version contains every year including and since 1969.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes