gh-129149: Add fast path for medium-sized integers in `PyLong_FromSsize_t()` (#129301)

The implementation of `PyLong_FromLong()`, `PyLong_FromLongLong()` and `PyLong_FromSsize_t()`
are now handled by a common macro `PYLONG_FROM_INT` which contains fast paths depending on the
size of the integer to convert. Consequently, `PyLong_FromSsize_t()` for medium-sized integers is faster
by roughly 25%.

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Co-authored-by: Sergey B Kirpichev <skirpichev@gmail.com>