Document builtin classes as such, not functions.
Closes #22507: document that PyType_IsSubtype does not call __subclasscheck__.
Closes #10031: overhaul the "imports" section of the programming FAQ.

Remove the advice to never use relative imports.
Remove the advice to locally import modules in __init__, it is a strange practice.
Remove the advice to use "from ... import *" with some modules.
Closes #14303: socket.makefile() does not call dup() anymore on the socket fd.
Issue #1686: Fix string.Template when overriding the pattern attribute.
Closes #17057: fix grammar in old-style vs new-style class docs.
Closes #16155: fix a few errors in doctest output of the FAQ pages.