Wire Up Code Coverage with CTS

[cwfitzgerald]

Now that we are running CTS in CI, we should make sure things count towards the coverage statistics, for whatever they are worth.

[andyleiserson]

I had this thought too. Both for coverage, and for the Mesa setup I mentioned in #7751 if we get the CTS working on Linux, it may be easier to merge the CTS job into the CI job rather than keep them as two separate workflows.