force_bytes() and force_unicode() now take a strings_only boolean

argument, which defaults to True for backwards-compatibility. When set

to False, these functions can take any arbitrary object and try to

turn it into a string.
force_bytes() will look for a __bytes__() dunder method, using that to

get the result, and then falling back on __str__().
force_unicode() will just look for __str__(). Since every object has

this, it will technically work with any object.
Typing has been updated to provide overloads based on the strings_only

parameter, helping to ensure callers receive type warnings if they

provide something other than a string without opting into

strings_only=False.
Unit tests have been added to cover this module.

Unit tests pass.
Tested this with some upcoming fixes for command output rendering.