Pub site search doesn't distinguish between dev dependencies and real dependencies

URL: https://pub.dartlang.org/packages?q=dependency%3Afront_end

In the link above `kernel` should not appear - it only has a dev_dependency on the front_end which is not a real dependency. Put another way, users with a dependency on the `kernel` package would not get a dependency on the `front_end` package, only developers of the `kernel` package would.

I think it would be fine to expose querying by dev dependency, but it shouldn't be treated the same as a regular dependency as it is an entirely different thing.