cargo-maeslstrom visualizes tests not run due to not being built

[bobbobbio]

Use Cases If I run cargo-maelstrom on some project, I expect it to attempt to run every test in the project, or else report why it wasn't able to. When cargo doesn't build a test artifact due to a disabled feature (or even some other reason we don't know about) cargo-maelstrom will just ignore any tests those artifacts have. This existing behavior matches how cargo test behaves, but we have any opportunity to do better.

see #359 where we disabled the warning

Acceptance Criteria If some test binary which matches the given filter isn't built, we produce some information about this in the test summary, saying something along the lines of "some unknown number of tests not run because binaries weren't built"

Definition of Done

• [ ] CHANGELOG.md updated.
• [ ] Documentation in doc/book/head updated.
• [ ] Issue is in the correct milestone.