It was not obvious from the type how many times the
final field of ClientReaderRequest would be invoked.
(Assuming it is invoked once per stream increment
results in a hang, which can be confusing.)
* Expose the max receive message length channel argument + unittest
* `ClientError` GADT ctor => `ClientErrorResponse`, expose `ClientError`
Prior to this commit, the name `ClientError` was both:
- The name of a data constructor name for the `ClientResult` GADT
- A name of an internal sum type for capturing different kinds of client
errors
We want to expose the latter to users of the library, and so expose the latter
and rename the former.
* Remove unused `MultiWayIf` lang ext
