* use instant::Instant everywhere * reexport instant::{Duration, Instant} from bevy_utils
* Switch from the deprecated `multitask` crate to `async-executor` * async-executor appears to be essentially multitask 0.3 * use block_on in futures_lite instead of pollster because futures_lite is already in the dependency list of async-executor
Fix for a bug (#449) in scheduler that could result in systems running concurrently when they shouldn't.
Reworked parallel executor to not block
