Expose all the "Routine building blocks" in public API

[mstechly]

@Brendan-Reid1991 asked:

At the bartiq top level, why do we expose PortDirection but not Port?

@mstechly answered:

I think that's because we never really needed it?
It is inconsistent, I agree.
I think we exposed publically the things that we actually needed for conversions in WB and Qualtran.
Now that I think about it, we exposed almost none of these things at the beginning.
But then it turned out we need to expose some of them to support writing some conversion code.
And now we ended up exposing more than not, so it looks weird.

Given the above, I think it would be reasonable to expose all the other "building blocks" classes in the public API.

[mstechly]

After discussion with @Brendan-Reid1991 and @dexter2206 , we decided that it 's probably better to change _routine to routine and have the following way for importing all the Port, PortDirection, ... objects:
from bartiq.routine import Port, PortDirection.

And remove them from the from bartiq import Port level.