command cargo test --list-test-name for shell completion

[loynoir]

Problem

#5759

#6645

rustup completions zsh cargo can only do static logic completion.

Unless cargo test --list-test-name, there is no way to have completion for dynamic logic.

Proposed Solution

cargo should expose test name logic

$ cargo test --list-test-name

Else, it's impossible to have test name shell completion.

Notes

No response

[epage]

Its not clear why this was created when #5759 exists. Closing in favor of that. If this is just for providing an alternative solution, let's keep that in the other issue. Ideally Issues are focused on problems and not solutions as we can then talk about multiple in one place, rather than having them scattered about.