[REM] *: remove various unused import shims

Before this commit, a lot of leftover import shims existed in the
codebase for py2-py3 compatibility, these are no longer needed since
Odoo 13.0+ doesn't support Python 2 anymore and is (finally) in EOL.

With this commit, these shims are dropped, making the code cleaner,
easier to read and with one less dependency.

Queue -> queue -> py2-py3 compatibility
xmlrpclib -> xmlrpc.client -> py2-py3 compatibility
ConfigParser -> configparser -> py2-py3 compatibility
itertools.izip_longest -> itertools.zip_longest -> py2-py3 compatibility
urllib -> urllib.request -> py2-py3 compatibility
__builtins__ -> builtins -> py2-py3 compatibility
_winreg -> winreg -> py2-py3 compatibility

mock -> unittest.mock -> merged into CPython

The debian/fedora packages and requirements.txt have been updated accordingly

closes odoo/odoo#44601

Related: odoo/enterprise#8141
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>