Adjust name of stable-mir-json downstream

[jberthold]

See runtimeverification/stable-mir-json#9 (comment)

A nix derivation for stable-mir-json has been added but it uses stable_mir_json (which is also the name that Cargo.toml configures).
Downstream dependencies need to adjust the name from stable-mir-json to stable_mir_json.

• in the Dockerfile.kmir in mir-semantics (where the link is created)
• in cargo.py in mir-semantics (hard-wired names and search preferences)
• in the kompass repository, Dockerfile and documentation