It's actually quite hard to build a front-end for fwupd at the moment
as you're never sure when the progress bar is going to zip back to 0%
and start all over again. Some plugins go 0..100% for write, others
go 0..100% for erase, then again for write, then *again* for verify.
By creating a helper object we can easily split up the progress of the
specific task, e.g. write_firmware().
We can encode at the plugin level "the erase takes 50% of the time, the
write takes 40% and the read takes 10%". This means we can have a
progressbar which goes up just once at a consistent speed.
Before this change calling FuUsbDevice->open() opened the device, and
also unconditionally added various GUIDs and InstanceIDs which we
normally do in setup.
Then fu_device_setup() would call the FuSubclass->setup() vfunc which
would have no way of either opting out of the FuUsbDevice->setup()-like
behaviour, or controlling if the parent class ->setup is run before or
after the subclass setup.
Split up FuUsbDevice->open() into clear ->open() and ->setup() phases
and add the parent class calls where appropriate.
This means that ->setup() now behaves the same as all the other vfuncs.
