Previously, we tested the `supported` methods of all drivers
sequentially in alphabetical order of file names. If you wanted to
extend a driver, the `supported` method of your driver could never be
tested if the one of its parent was tested first.
We've now added a priority order to drivers so that by default the
extending driver will always be tested before the extended driver.
You can still do something similar to what `is_tested_last` did by
manually setting the priority of a driver to 0.
Ex: The way barcode scanners is really similar to keyboards, but still
requires a few modifications in the driver. We couldn't extend the
keyboard driver easily because the supported method of barcode scanners
had to be more strict than the one of keyboards. If the
KeyboardUSBDriver was tested first, scanners were recognized as
keyboard and didn't have all the specific features of scanners.
TaskID: 2082282