Added :meth:`cache.mkdir() <pytest.Cache.mkdir>`, which is similar to the existing :meth:`cache.makedir() <pytest.Cache.makedir>`,
but returns a :class:`pathlib.Path` instead of a legacy ``py.path.local``.

Added a ``paths`` type to :meth:`parser.addini() <pytest.Parser.addini>`,
as in ``parser.addini("mypaths", "my paths", type="paths")``,
which is similar to the existing ``pathlist``,
but returns a list of :class:`pathlib.Path` instead of legacy ``py.path.local``.