Allow for preventing reset during interactive tests

**Is your feature request related to a problem? Please describe.**
Similar to #655
I would like to be able to run a few tests in my e2e and a few tests in my components and see the coverage report for those tests from interactive mode. I currently manually reset the coverage when I need to.

**Describe the solution you'd like**
I'd like to set a config flag that simply prevents the reset so I can reset things manually when I want to.

**Describe alternatives you've considered**
I currently have my own coverage plugin to get around this issue, but I'd like to switch to this plugin.

**Additional context**
My current solution:
https://github.com/RoundingWell/care-ops-frontend/blob/develop/test/plugins/coverage.js#L20