forward internal errors instead of timeout status codes

[trivalik]

Fixes #236

The only question for me is should we leave the _exception list filled with the exception or can we consume it.

[awcullen]

As you commented, this won't be needed if we use GetPendingException.

[awcullen]

We should consume the exception. May I suggest:

using (var timeoutCts = new CancellationTokenSource((int)request.RequestHeader!.TimeoutHint))
using (var linkedCts = CancellationTokenSource.CreateLinkedTokenSource(timeoutCts.Token, _channelCts.Token, token))
using (var registration = linkedCts.Token.Register(o => ((ServiceOperation)o!).TrySetException(GetPendingException() ?? new ServiceResultException(StatusCodes.BadRequestTimeout)), operation, false))
{

[trivalik]

@awcullen you missed to remove PeakFirstPendingException()

Is there a release planed?

[trivalik]

@awcullen is there a planned to push a release to nuget.org?