Generate cargo dependencies file with dd-rust-license-tool

https://github.com/DataDog/rust-license-tool/

Looks much more tidy.

The issue provides only the dd-rust-license-tool repository link and does not name a file, test, or entry point. First inspect the repository's existing dependency and license-file setup, then compare the tool's generated output with the project's needs. Done means a generated Cargo dependencies file is added in the expected location and its contents are tidy.

Written by the indexing model from the issue text.