This fixes an issue where pylint complains about missing implementations
of abstract methods in subclasses of `File` which only override
`collect()` (as they should).
It is also cleaner and makes sense, these methods really don't need to
be overridden.
The previous methods defined directly on `FSCollector` and `Package` are
deprecated, to be removed in pytest 7.
See commits e2934c3f8c and
f10ab021e2 for reference.
Ran Benita