Task: reimplement FOSSA check in CI

[deepthi]

In #14119, we removed the FOSSA check because it was exposing an API key (which has since been revoked). This needs to be re-implemented with the API key being stored in a secure way - i.e. as a secret in GH, preferably at the org level.

[deepthi]

From CNCF:

added the secret as FOSSA_API_KEY to the Org (All Repos)

So we can go ahead and add the workflow back using this secret.

[mattlord]

Noting that I will re-enable it along with adding codecov: #14326