Move uses of to_bytes, to_text, to_native to use the module_utils version (#17423)

We couldn't copy to_unicode, to_bytes, to_str into module_utils because
of licensing.  So once created it we had two sets of functions that did
the same things but had different implementations.  To remedy that, this
change removes the ansible.utils.unicode versions of those functions.

docsite/rst/developing_modules_python3.rst

@@ -215,6 +215,28 @@ Python3.  We'll need to gather experience to see if this is going to work out
 well for modules as well or if we should give the module_utils API explicit
 switches so that modules can choose to operate with text type all of the time.
 
+Helpers
+~~~~~~~
+
+For converting between bytes, text, and native strings we have three helper
+functions.  These are :func:`ansible.module_utils._text.to_bytes`,
+:func:`ansible.module_utils._text.to_native`, and
+:func:`ansible.module_utils._text.to_text`.  These are similar to using
+``bytes.decode()`` and ``unicode.encode()`` with a few differences.
+
+* By default they try very hard not to traceback.
+* The default encoding is "utf-8"
+* There are two error strategies that don't correspond one-to-one with
+  a python codec error handler.  These are ``surrogate_or_strict`` and
+  ``surrogate_or_replace``.  ``surrogate_or_strict`` will use the ``surrogateescape``
+  error handler if available (mostly on python3) or strict if not.  It is most
+  appropriate to use when dealing with something that needs to round trip its
+  value like file paths database keys, etc.  Without ``surrogateescape`` the best
+  thing these values can do is generate a traceback that our code can catch
+  and decide how to show an error message.  ``surrogate_or_replace`` is for
+  when a value is going to be displayed to the user.  If the
+  ``surrogateescape`` error handler is not present, it will replace
+  undecodable byte sequences with a replacement character.
 
 ================================
 Porting Core Ansible to Python 3