Improve composer test efficiency

[ethanoroshiba]

@Fraser999 pointed out that this line has the potential to introduce delay even if initialization is already complete, due to sleeping before the if statement:

astria/crates/astria-composer/tests/blackbox/helper/mod.rs

Line 202 in 8879aaf

tokio::time::sleep(Duration::from_secs(1)).await;

The proposed solution is to change to tokio::task::yield_now().await;, which greatly improves the speed of many tests, but causes some others to fail, which will need to be reevaluated.

┆Issue Number: ENG-1074