Fix #230: Modify Barrier::wait to return BarrierWaitResult

[r1ru]

To make the current implementation of Barrier API compatible with other libraries like tokio, following changes were made.

1. Modified Barrier::wait to return BarrierWaitResult
2. Removed unnecessary Arc since it is common to use Barrier struct wrapped with Arc

See
https://doc.rust-lang.org/beta/std/sync/struct.Barrier.html
https://docs.rs/tokio/latest/tokio/sync/struct.Barrier.html

[veqcc]

@r1ru
Could you write the description of this PR?
I do not recognize what is the problem and why this change is needed.

[ytakano]

Can you add test code like this?

awkernel/awkernel_async_lib/src/sync/mutex.rs

Line 116 in 29c3d31

fn test_simple_async_mutex() {