Keeping start info records sorted

The documentation states that records should be sorted, but we do
some additional work as if it was not sorted. Update logic to both
ensure that the list stays sorted, and reduce the unnecessary
sorting.

Test: run appstartinfo unit tests which cover order with flag enabled and disabled
Bug: 384539178
Flag: android.app.app_start_info_keep_records_sorted
Change-Id: I34637a6f4fddf7e86f4b87dfde062478a9036057