[3.8] bpo-39562: Prevent collision of future and compiler flags (GH-19230) (GH-19835)

[3.8] bpo-39562: Prevent collision of future and compiler flags (GH-19230) (GH-19835)

The constant values of future flags in the __future__ module
is updated in order to prevent collision with compiler flags.
Previously PyCF_ALLOW_TOP_LEVEL_AWAIT was clashing
with CO_FUTURE_DIVISION..
(cherry picked from commit 4454057269b995341b04d13f0bf97f96080f27d0)

Co-authored-by: Batuhan Taşkaya <batuhanosmantaskaya@gmail.com>