bpo-29341: Clarify that path-like objects are accepted in some os methods (GH-10101)

bpo-29341: Clarify that path-like objects are accepted in some os methods (GH-10101)

Some methods in the os module can accept path-like objects. This is documented in the general documentation but not in the function docstrings. To keep both in sync, the docstrings need to be updated to reflect that path-like objects are also accepted.