chore: switch from Coveralls to Codecov

[mark-wiemer]

PR Checklist

• Addresses an existing open issue: fixes 🛠 Repo: Coveralls outages causing CI to fail #5436
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Codecov provides the same functionality in much the same way, just a different backing company and a different coverage dashboard UX. This PR updates relevant artifacts:

• use Codecov task
• use Codecov coverage badge in readme
• link to Codecov dashboard from mochajs.org
• adds instructions for how to set up Codecov with OIDC for contributors' forks

Validations (in progress):

• happy path works
• fails the pipeline when the task fails
• works on PRs by non-maintainers

[mark-wiemer]

Closing this in favor of migrating to Codecov, see original issue #5436

[mark-wiemer]

• Run triggered from PR
• Run triggered manually

Notes:

• Triggered from PR isn't logging the coverage token and failing accordingly. This mostly aligns with the docs: "They are not passed to workflows that are triggered by a pull request from a fork." But this isn't from a fork
• Coveralls did not use a secret, we probably had some link in an account on their side
• I'm sure this is a common issue that I'll figure out soon enough :)

[codecov]

Welcome to Codecov 🎉

Once you merge this PR into your default branch, you're all set! Codecov will compare coverage reports and display results in all future pull requests.

Thanks for integrating Codecov - We've got you covered ☂️

[MarkWiemer]

• Before adding Codecov app: 500
• After adding Codecov app: 200 :)
• Sample Codecov report from a fork

[mark-wiemer]

(@MarkWiemer is my alt acct not a fraud I promise)