Code coverage using Cloverage

[dundalek]

I created a proof-of-concept integration: https://github.com/dundalek/lazytest-cloverage

The test output prints a summary table:

And then the HTML report shows details for namespaces:

Open questions:

1. What should be the entrypoint?
   There could be special one like lazytest.cloverage, or we could have the usual lazytest.main but with some option to enable coverage.

2. How to pass options to cloverage?
   We can have sensible defaults to print the summary and generate HTML report, but there are other options for cloverage, mainly to generate reports in additional formats like codecov, coveralls, lcov, junit, etc. for CI.

3. Improve how paths and namespaces are wired together.
   Instead of duplicating options which can lead to inconsistencies, we would ideally use lazytest mechanism to determine paths and namespaces and then pass those to cloverage.