RFC: Output - Multi-harness runner with progression

[adpaco-aws]

Requested feature: The current harness runner is built on top of the previous single-harness runner we had. There's lots to improve in terms of UX here, starting from a distributed design which allows us to decouple harness runners from the main Kani driver. Progression is another area to improve: We could show dot-based progress similar to how it's done other tools (e.g., cargo test -q), but with more colors to represent a wider set of states (unwinding, SAT-solving, etc.).

Use case: Running multiple harnesses.
Link to relevant documentation (Rust reference, Nomicon, RFC): cargo test - display options

Test case:

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