Decide if methods that create asynchronous instruments should return an object or not

[ocelotl]

Can someone make a separate issue for this documenting what other languages are doing? I had a look at Java and the builder will return an instrument handle: https://github.com/open-telemetry/opentelemetry-java/blob/5ff5f3f494fe6958574acff0e8c59bc013b69dad/api/all/src/main/java/io/opentelemetry/api/metrics/LongCounterBuilder.java#L54

Originally posted by @aabmass in #2339 (comment)

[ocelotl]

I think it is better to return an instrument. I understand that an asynchronous instrument itself has no functionality available for the user but I see no point in "hiding" it from the user.

The instruments also have attributes that the user may want to access like name, description and unit.

[aabmass]

See also open-telemetry/opentelemetry-specification#2281

[ocelotl]

We are already returning an instrument regardless of it being synchronous or not, closing.