Refactor code coverage logic into independent lib

[bootstraponline]

Hey,

Is there any interest in refactoring the code coverage logic (conversion & reporting) out into an independent lib? We use phab with buildkite and not Jenkins, however much of the code can be reused if the Jenkins dependencies are removed.

I'm currently forking some of the logic in this prototype repo:
https://github.com/bootstraponline/bazel_example