Every place where a type/function name is used in a Humility API should allow fully-qualified names.

[cbiffle]

Rust programs often use the same name in different modules, because we have modules/namespaces. e.g. a typical program will contain many types named Error in different places.

Humility originally stripped crate/module path information off types, and used unqualified names. This has been causing problems for a while in things like processing Idol interfaces -- see oxidecomputer/hubris#1896 for the most recent case.

I added partial support for fully qualified names back in 2021, but we need to complete the switch-over. It's okay to allow unqualified names in some cases (particularly in the TUI!) but that should be a convenience, which turns into an error if the name is ambiguous. At that point the user should always be able to provide a fully qualified name.