Duplicate annotations

[seebees]

Duplicate annotations are complicated.
It is not clear which annotation is going to be covered by which test.
While it would be nice to require only a single annotation
this may be overly restrictive.

Perhaps an additional property could be added?
Similar to //= type=test we could have something like //= dedup=my-arbitrary-string.
Obviously dedup is a poor name,
but having the flexibility put annotations in multiple locations
could be a requirement if the specification can not be adjusted.