Usage of toolchains_rust in other modules

[umaucher]

In the scope of eclipse-score/persistency#137 the toolchain is added to persistency can you describe more detailed about the usage of it?

Open questions:

• needs in the MODULE.bazel to get it working? bazel parameter / configuration to use it (or then also using one of the existing configurations (rust toolchain from "official" bazel registry)
• Is it planned to have the toolchain as such (aka SDP) provided and used in the scope of an official S-CORE repository?