Reimplement Fetch

[grtcdr]

In version 5.0, the Linux implementation of Fetch was removed so it could be reworked. It will now be reimplemented but with performance in mind.

What must be done different?

• Fetch::fetch_by_class() in previous versions would create a PCIDevice out of every PCI device it could find, then and only then, does it remove the irrelevant PCI devices, and this costs time and is so inefficient it literally blows my mind why I decided to implement it the way I did.

Nice-To-Haves

• A new method, something along the lines of Fetch::fetch_by_subclass(name) where name is of type String. This method should return only the PCI devices whose subclass (click any click to see subclasses) is equal to what was provided to the method. It is unmaintainable for me to provide an enum with ready-to-use subclasses, because there's well over 50 of these, and they're always changing.

[grtcdr]

#8 solves this