Tests if packages imported by subpackages/external packages use different instances.
Package output:
Interval A: 8
Interval B: 8
Interval External: 8
Interval A set to 15
Interval A: 15
Interval B: 15
Interval External: 15
Interval B set to 20
Interval A: 20
Interval B: 20
Interval External: 20
Interval External set to 25
Interval A: 25
Interval B: 25
Interval External: 25