Add cargo deny to CI

[iamjpotts]

1. Locks the list of allowed licenses to the current set of dependency licenses
2. Surfaces two advisories as warnings (comments added to deny.yml for both)
3. Surfaces duplicate versions of the same dependency as warnings (comments added to deny.yml for both)

One of the advisories is for atty a dependency of criterion and tracked in an issue in the criterion repo.

[vmx]

Thanks for your PR! I've just merged a PR that fixes the Clippy errors on CI. Could you please rebase your PR? I think it's a good idea and we should give it a try. If it turns out a too big burden, we can always remove it again. Also thanks for adding the exception for the current problems, so that we can start in a "green" state and work from there.

[iamjpotts]

Thanks for your PR! I've just merged a PR that fixes the Clippy errors on CI. Could you please rebase your PR? I think it's a good idea and we should give it a try. If it turns out a too big burden, we can always remove it again. Also thanks for adding the exception for the current problems, so that we can start in a "green" state and work from there.

@vmx

Rebased, and made a change to the workflow job to how it installs cargo-deny.

[vmx]

Thanks for spending so much time on this!