This commit replaces calls to pycompat helpers that were intended for
python 2 <-> python 3 interoperability for python 3 builtins, as python
2 is no longer officially supported by Odoo.

This includes:
    * calls to imap/izip/ifilter replaced by map/zip/filter
    * uses of text_type replaced by str
    * uses of unichr replaced by chr
    * calls to implements_to_string, implements_iterator removed
    * string_types and integer_types replaced by str, int respectively
    * calls to to_native replaced by calls to to_text

This is done in preparation to the removal of these deprecated helpers
in the following commit.

Closes #20391

In Python 3:

* various builtins and dict methods were changed to return
  view/iterable objects rather than lists
* and the separate Python 2 view/iterable builtins and methods were
  removed altogether

This is problematic when using these items as list (which the happens
repeatedly in Odoo), but more viciously when iterating *multiple times*
over them (which also happens, which I've messed up multiple times while
writing this, and which is a pain to debug even when you've just created
the issue).

Convert all code using these to semantics-matching cross-version
helper functions to get the LCD behaviour between P2 and P3, and
forbid the builtins via lint.

issue #8530

In Python 3, ``print`` becomes a builtin function. This is available
in Python 2 by importing the ``print_function`` feature from
``__future__``, the feature is conveniently still available in Python
3 (it just does nothing).

Fixers:
    libfuturize.fixes.fix_print_with_import

#8530

Demoted to library in Python 3, see if uses can be replaced by more
specific construct, just import functools.reduce otherwise.

Futurize fixers:
* lib2to3.fixes.fix_reduce