API: Consider removing `Tracer.create_span()`

[carlosalberto]

Have been reviewing other languages' implementations and it seems there's no way to create non-started Spans.

My take would be on removing the Tracer.create_span() method (at least from the API), to reduce API surface. It also feels like one of the cases where it makes sense to put it back in the API if/when we have a real need for it.

However, I remember the OC crew mentioning why it was needed in Python. Anybody would like to chime in?

[Oberon00]

See also #97 (comment)

[codeboten]

Is the plan to go ahead and remove create_span from the API?

[carlosalberto]

@codeboten Yeah, as far as I remember, while keeping it in the SDK ;)