Make tidy complain if the Cargo.lock files are incompatible

[jdm]

I'm having trouble articulating the things in particular we want to check, but I want to prevent problems like #5433 (comment) upfront. If you could look at commits and see if there was a change to a Cargo.lock file but no change to the other ones, that would be useful.

[kmcallister]

This can also check for multiple versions of a library within a single build.

It should be easy to use the same TOML parser as Cargo itself.

[Ms2ger]

#3360