bumpalo has use-after-free due to a lifetime error in `Vec::into_iter()`

Summary

In affected versions of this crate, the lifetime of the iterator produced by `Vec::into_iter()` is not constrained to the lifetime of the `Bump` that allocated the vector's memory. Using the iterator after the `Bump` is dropped causes use-after-free accesses.

The following example demonstrates memory corruption arising from a misuse of this unsoundness.

```rust use bumpalo::{collections::Vec, Bump};

fn main() { let bump = Bump::new(); let mut vec = Vec::new_in(&bump); vec.extend([0x01u8; 32]); let into_iter = vec.into_iter(); drop(bump);

for _ in 0..100 { let reuse_bump = Bump::new(); let _reuse_alloc = reuse_bump.alloc([0x41u8; 10]); }

for x in into_iter { print!("0x{:02x} ", x); } println!(); } ```

The issue was corrected in version 3.11.1 by adding a lifetime to the `IntoIter` type, and updating the signature of `Vec::into_iter()` to constrain this lifetime.