[feature request] extend "Rust Analyzer: Run" to include `test-mod` when _outside_ `mod tests`

[japaric]

Current behavior:

// A

pub fn api() { /* .. */ }

fn helper() { /* .. */ }

#[cfg(test)]
mod tests {
    // B
    use super::*;

    #[test]
    fn api_works() { /* .. */ }
    // even more tests
}

invoking "Rust Analyzer: Run" from scope B includes a test-mod option to run the unit tests in mod tests
invoking "Rust Analyzer: Run" from scope A does not include a test-mod option to run the unit tests in mod tests

Desired behavior: I would like the test-mod option to be available when invoking "Rust Analyzer: Run" from scope A.

Use case: you may in the middle of editing helper and want to run tests that exercise api, which calls helper. "Peek/run related tests" won't get you there. This extension would help with that.