Add no-op processor

[pellared]

Blocked by:

• https://github.com/open-telemetry/opentelemetry-specification/pull/4067

Here is another usage of an no-op processor in a processor implementation.

I think we can think about adding it the the SDK as it can be commonly used in processor decorators.

See also: https://github.com/open-telemetry/opentelemetry-go-contrib/pull/5817#discussion_r1658924196

Originally posted by @pellared in https://github.com/open-telemetry/opentelemetry-go-contrib/pull/5861#discussion_r1666640564

From https://github.com/open-telemetry/opentelemetry-specification/pull/4090#discussion_r1659220349:

It is always implied that implementations can go beyond the spec. If there is no desire to ensure common implementation, adding this only adds cruft and potential confusion.

As far as I understand, adding a no-op processor to the SDK would not make the it not compliant with the specification (the SDK should be still compliant).

[pellared]

I suggest to postpone until https://github.com/open-telemetry/opentelemetry-specification/pull/4067 is resolved.