Bugfix suspended computation blocks

[nomisRev]

1. KotlinX Coroutines throws CancellationException with cause when propagating cancellation by exception from async to it's parent. Since we cause the CancellationException with ShortCircuit we need to look if ShortCircuit can be found within the causes to return the excepted shifted value. If the cancellation is immediate, then it doesn't wrap in CancellationException, that caused the test to be flaky. Now it passes consitently on a loop.

2. Suspended computation blocks were running on EmptyCoroutineContext, they need to run on the parents ctx to correctly propogate the state from outside to inside the computation block.

[raulraja]

Thanks @nomisRev !

[i-walker]

Thanks, @nomisRev for the nice explanation!