License check runs for workspace crates

[jplatte]

cargo deny licenses checks every crate, even those in the workspace / the crate from Cargo.toml for non-workspace crates. I would expect the licenses check to only run on dependencies.

This is made worse by the fact that I can't put unlicensed = "allow" under an item in exceptions.

[Jake-Shadle]

If you have unlicensed workspace/local crates, you can currently mark them as publish = false and set

[license]
private = { ignore = true }

to avoid checking them, but having a workspace = ignore would be a good enhancement.