Optimize the Fraction class arithmetics for small components

[skirpichev]

After #24779 there are some speed regressions, which can be solved by using private attributes in magic methods.

Also, right now the fractions module code is using sometimes private attributes (_numerator and _denominator, e.g. in the __int__) and sometimes - public (numerator and denominator, e.g. in the __floor__). This looks not very consistent, at least.

Linked PRs

• gh-91851: Micro optimizations for Fraction's arithmetic #25518
• gh-91851: Trivial optimizations in Fraction #100791