Is your feature request related to a problem? Please describe.
Issue #9599 wants to add enqueuedTime to the message link. But AbstractSpan.link(cls, traceparent) doesn't accept attributes.

Describe the solution you'd like
I suggest change AbstractSpan.link(cls, traceparent) to:

AbstractSpan.link(cls, traceparent, attributes=None):

Describe alternatives you've considered
Change AbstractSpan.link(cls, traceparent) to:

AbstractSpan.link(cls, traceparent, attributes=None) -> Link:

But this unnecessarily exposes the Link object, which could be from opencensus or opentelemetry.

Additional context
None