Parallelize `test` step in cicd

[mugbug]

What could be improved

Based on this issue: #954, I noticed that we could also go for the same approach for the packages' unit/widget tests execution, and run each package tests in parallel.

Why should this be improved

• When tests fail, it isn't that easy to know which package was the cause. It requires a deeper look inside the workflow logs. Making the tests run in parallel, that will be easily visible from the PR checks
• It'll probably decrease some seconds or even minutes from the cicd workflow execution, and we can add many more tests on smaller packages and don't increase this execution time.

Any risks?

None AFAIK

More information

This implementation should be pretty similar to this one: #1029

Also, I'd be happy to help with this one as well, but it seems to be a pretty nice good first issue for new contributors =]

[erickzanardo]

That would be awesome!

[spydon]

@mugbug now when hacktoberfest is over I don't think any newcomers will pick this up, do you want to do it? :)

[mugbug]

For sure! I'm just a little busy these days, but as soon as I have some free time I'll take a look on this 🙂

[spydon]

Kind of solved with Spec.