Incident management - shifts are not displayed correctly

The on-call schedule timeline bars that display shifts are in the wrong place - both offset and of an incorrect width.

This was introduced in the timeline refactor: !58204 (merged) / !58322 (merged) / #324608 (closed)

Reproduction steps

1. Ensure you have an existing on-call schedule.
2. Create a new rotation. Ensure that it has:
   • an active period that overlaps your local midnight. e.g. 8pm to 4am.
   • at least a few days in length.
3. View the '1 day' view for your schedule.
4. Navigate a few days forwards into the rotation.

Expected behavior

1. You'll see the end of the previous day's shift, and the start of the next day's shift.

Actual behavior

1. Only the end of the previous day's shift is shown.
2. The shift is offset by an amount and no longer lines up correctly with the underlying data.

Screenshots:

expected	actual

tooltip showing shift data.