fix(transport): rework trait bounds

[rvolosatovs]

Unfortunately, plain &[&[Option<usize>]] path bounds do not accept Arc<[Arc<[Option<usize>]>]> values, which users would likely use, especially in dynamic use cases. On top of that, lack of 'static lifetime on the stream returned by serve prevents it from being passed into e.g. tokio::spawn.
Rework trait bounds to address these issues.

Thanks @LUK3ARK for reporting!