replace unused cargo-deny check with a new cargo-deny-licenses job (#13956)

* ci: remove the cargo-deny job

It's been broken and disabled for quite a while, and per internal
discussion there doesn't seem to be any interest in fixing it and
actually using the job output for anything.

* ci: add new cargo-deny-licenses job

It'll run on all PRs and fail if external dependencies with unsuitable
licenses are detected.