[ty] Implement Python's floor division semantics for `Literal` `int`s (#18249)
Division works differently in Python than in Rust. If the result is
negative and there is a remainder, the division rounds down (instead of
towards zero). The remainder needs to be adjusted to compensate so that
`(lhs // rhs) * rhs + (lhs % rhs) == lhs`.
Fixes astral-sh/ty#481.