[3.15] gh-153200: Fix math.isqrt() for int subclasses with overridden comparison...

[3.15] gh-153200: Fix math.isqrt() for int subclasses with overridden comparison operators (GH-153203) (GH-153223)

The final check-and-correct comparison in the arbitrary precision path
could call a comparison operator overridden in an int subclass.
Compare by value with int's tp_richcompare.
(cherry picked from commit 3a1b5473f217fc493f743c9ca8b877d2e76f8e6b)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>