Improving source replacement in debian/bin/cargo

The prepare-debian command on the cargo wrapper sets all the required flags for building the code correctly, while also replacing the crates-io source by a vendor directory.

This is a static check that do not account for crates coming from other sources, such as git or custom registries. Despite uncommon, those sources can happen and should be addressed.

This patch modifies the prepare-debian command to also parse the Cargo.lock file, if CARGO_LOCK is specified, in order to check for those alternative sources and also replace them in the generated config.toml file.