Selecting between relative and absolute time tracking

The switch also needs to select between using absolute time as opposed to the absolute time relative to the first turn reference time (see the Bmad documentation on `bmad_com%absolute_time_ref_shift`).

No repository file or test is named. Start by locating the switch that selects time tracking and read the Bmad documentation for `bmad_com%absolute_time_ref_shift`; confirm how the first-turn reference time is represented. Done means the switch clearly selects absolute time or time relative to that reference, with coverage for both choices.

Written by the indexing model from the issue text.