Allocator: allocate from failible iterator

`Alocator::allocate_from_iterator` lets us create an allocation from an iterator, but this doesn't work when we want to stop iterator if an error happens. Ideally, there would be a separate method:

```rust
fn try_allocate_from_iterator(nrows: R, ncols: C, iter: I) -> Result
where I: IntoIterator>;
```

This would abort and bubble up the first error from the iterator.