Also add slightly richer parse errors now that we can include a string
literal with returned errors.
This will allow us to use TRY() when working with JSON data.
We now expose the `USBDevice`'s address in the SysFS object. This means
that device addresses are no longer determined by the name of the file
in the `/bus/usb/` directory. This was an incorrect way of determining
device address, as a standard PC can have multiple USB controllers
(and hence multiple buses) that can have overlapping device IDs.
