This allows us to find out the logical parent device, for instance in composite
devices with more than one firmware image for a single device.
We also allow lazily specifying the device parent using a GUID and the engine
then automatically sets the parent object when the GUIDs match, which allows
children and parents to exist in different plugins.
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 allows us to show the devices in a GUI with a nice icon. Some of the icon
mappings are not perfect and I'll be asking the GNOME designers for some
additions to the icon specification.
Custom vendor icons can also be specified, and /usr/share/fwupd/icons would be
a good place to put them. If vendor icons are used they should show a physical
device with the branding, rather than just the vendor logo.
Although we supported other hashes than SHA1 (which is now moderately unsafe)
we had to switch the metadata provider and daemon on some kind of flag day to
using SHA256. Since that's somewhat impractical, just allow multiple checksums
to be set on objects and just try to match whatever is given in preference
order.
This also means we can easily transition to other hash types in the future.
The removed API was never present in a tarball release, so not an API break.
