tristate features will automatically disable if dependencies marked
as required are missing.
Packagers can manually override using `auto_features`.
Link: https://mesonbuild.com/Build-options.html#features
It's a common action for plugins to call FuUsbDevice->open() then claim
interfaces, and then release them just before FuUsbDevice->close().
It's also something a lot of plugins get wrong, so provide common code
to handle it correctly in one place.
We were calling g_module_symbol() 2703 times, which is actually more
expensive than you'd think.
It also means the plugins are actually what we tell people they are:
A set of vfuncs that get run. The reality before that they were dlsym'd
functions that get called at pretty random times.
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.
