Merge from 3.3: Add a str class entry to the string section (issue #16209).

This commit also moves the documentation for the str built-in function to
the new class entry.  Links to :class:`str` now go to the class entry with
the string methods immediately afterwards.

diff --cc Doc/c-api/object.rst
Simple merge

diff --cc Doc/reference/datamodel.rst
Simple merge

diff --cc Misc/NEWS
index eb3a98d49785c8dc82ef15286cbb24313ac23b6a,cd77da867614e7a9edbca87b8c9fb2e2bea0131e..2dff7b17ca8db187095e4086aeb23fcc2d59147b
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -418,10 -286,19 +418,13 @@@ Buil
  Documentation
  -------------
  
+ - Issue #16209: Move the documentation for the str built-in function to a new
+   str class entry in the "Text Sequence Type" section.
+ 
  - Issue #13538: Improve str() and object.__str__() documentation.
  
 -- Issue #16489: Make it clearer that importlib.find_loader() requires any and
 -  all packages to be separately imported.
 +- Issue #16489: Make it clearer that importlib.find_loader() needs parent
 +  packages to be explicitly imported.
  
  - Issue #16400: Update the description of which versions of a given package
    PyPI displays.