Generating additional windows does not keep opportunities sorted

[Mark2000]

Describe the bug
The opportunities list is expected to be sorted by close time. It is possible to break this.

To Reproduce
Steps to reproduce the behavior:

1. Generate two segments of opportunities (as opposed to all at once).
2. Observe the order of the opportunities list; it is not sorted around the time where the two opportunity generations met.

Expected behavior
Opportunities should always remain sorted.

Additional context
I suspect this comes from not properly reordering opportunities when one of the form [opportunity_start, opportunity_generation_end_time] is extended to [opportunity_start, opportunity_end]. For now, just generate all of your opportunities at once to avoid this issue.