Test runner: Ability to customize test command

[ytham]

Check for existing issues

• Completed

Describe the feature

I'd like the ability to customize the test runner command so that it can display backtraces. Right now, when I click the ▷ symbol next to a Rust test, it will run

cargo test -p <crate> <testname> -- --nocapture

But it'd sure be nice to be able to add/remove flags, tmp env vars, etc.

If applicable, add mockups / screenshots to help present your vision of the feature

No response