API consistency for GPIO types

[MabezDev]

We should ensure that all our GPIO types have a consistent API across them all.

This may include making the Output/Input traits public again.

Related to #1995

[bugadani]

This may include making the Output/Input traits public again.

Which traits are you referring to? InputPin and OutputPin are still public.

[Dominaezzz]

The APIs on them aren't public in a meaningful way. They have the crate::Internal param to prevent users from using them directly.

[bugadani]

Right. Well, things will change.