When scanning for network adapters, we give each driver a chance to
claim the PCI device and whoever claims it first gets to keep it.
Before this patch, the driver API returned a LockRefPtr<AdapterType>,
which made it impossible to propagate errors that occurred during
detection and/or initialization.
This patch changes the API so that errors can bubble all the way out
the PCI enumeration in NetworkingManagement::initialize() where we
perform all the network adapter auto-detection on boot.
When we eventually start to support hot-plugging network adapter in the
future, it will be even more important to propagate errors instead of
swallowing them.
Importantly, before this patch, some errors were "handled" by panicking
the kernel. This is no longer the case.
7 FIXMEs were killed in the making of this commit. :^)
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