Remove "sync" feature(s)

[uklotzde]

Bundling an opinionated synchronous API wrapper around the native, asynchronous API is unfortunate and wrong. It only causes trouble and misunderstandings. I recommend to remove it before releasing version 1.0.

If users need synchronous communication they should use a different library.

[vfiack]

If users need synchronous communication they should use a different library.

Do you have one to suggest?

[uklotzde]

If users need synchronous communication they should use a different library.

Do you have one to suggest?

Unfortunately not.

Re-implementing the sync client(s) by reusing common parts from frame and codec but without the unnecessary Frankenstein-ean loop through the Tokio runtime would be the path forward.