coroutine.yield should stay infinitely yielding until the thread is resumed

[sasial-dev]

coroutine.yield should stay infinitely yielding until the thread is resumed, an example can be found in this simple repro:

#[tokio::test]
async fn test_yield() {
    let mut runtime = lune::Runtime::new();
    runtime.run("zap", "coroutine.yield()").await.unwrap();
}

I reproduced this off master:

[dependencies]
# current master commit at the time of writing this issue
lune = { git = "https://github.com/lune-org/lune.git", rev = "5d1401cdf611cc9f215f03bdf16ada0e77717edf" }
tokio = { version = "1", features = ["full"] }

This has stopped us from having e2e testing for zap so far as the coroutine should stay yielding until it "receives" data.