Add Cargo.lock to repository

[Elarnon]

As https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
says:

If you’re building a non-end product, such as a rust library that
other rust packages will depend on, put Cargo.lock in your .gitignore.
If you’re building an end product, which are executable like
command-line tool or an application, or a system library with crate-type
of staticlib or cdylib, check Cargo.lock into git.

Technically telamon (the crate) is a library, but its only users are
the kernels and telamon-capi crates, which are respectively used
through command-line tools and a system .so cdylib. Hence there are no
good reasons not to keep the Cargo.lock in the repository, at least
until the day (if it comes) there are other Rust packages (outside of
this repo) which use telamon (the crate).

This allows to have shared, known-working dependency versions across
developers and machines.