Add `is_integer` to fractions.Fraction

[hauntsaninja]

Requested by @mdickinson in #100268 (comment)

The case for:

• Improves duck type compatibility between Fraction and float (and now int)
• Simple to implement; hopefully low maintenance cost

The case against:

• Not aware of much demand for it from users
• The case for int.is_integer is much stronger, since the PEP 484 type system conflates float and int | float

Linked PRs

• gh-100488: Add is_integer method to fractions.Fraction #100489