It only remained on FwupdResult because I couldn't make up my mind about whether
it was a property of the device, or the firmware release. It's more logically
the latter, as you could have a .cab file with multiple versions of the
firmware and only the first being signed.
This was only ever added for gnome-software, and is too inflexible for anything
else. It turns out we don't even need it in GNOME, as we can construct a
suitable ID ourselves using the existing values.
It was also ambiguous whether the unique ID was in reference to the device
or release -- and for gnome-software we need both.
It only remained on FwupdResult because I couldn't make up my mind about whether
it was a property of the device, or the firmware release. It's more logically
the former, and that's how plugins are using it.
This does two things:
* Allows new users of the library to see only the supported symbols
* Allows us to ensure we're not using deprecated API internally
I can also use this in gnome-software in CI to make sure we're not using
deprecated API too. I don't think we're ready for a soname bump so we have to
hang on to the deprecated code for now.