Add code coverage reports and checks on PRs

[BigLep]

Done Criteria

When a PR is opened:

1. the author and reviewers can visually see how many of edited or new lines have code coverage
2. ensure that new code has a certain amount of code coverage

Why Important

1. As Lotus moves to more frequent releases and usually doing network-upgrade releases from master rather than the last production release (docs), there is extra importance on ensuring code in master is well tested.
2. This is a lens to help authors get feedback on their code without taking reviewer time

User/Customer

Maintainers

Notes

1. What level of code coverage required for new code is TBD.
2. I should dig up this repo's history with code coverage in the past.