Fix a number of OTel tracing issues

[glbrntt]

Motivation:

The OTel tracing interceptors had a number of issues. The most important was that spans were ended too early in their lifecycle. Others included not always setting the span status or grpc status code attribute.

Modifications:

• Start and end spans manually
• Replace the hooked async sequence with custom sequnces for server request messages and client response messages. This allows the atomic to be dropped in favour of a simple integer stored on the iterator.
• Replace the hooked async writer with a more targeted tracing writer

Result:

Tracing interceptors are more reliable