Auto merge of #105046 - scottmcm:vecdeque-vs-vec, r=Mark-Simulacrum

Send `VecDeque::from_iter` via `Vec::from_iter`

Since it's O(1) to convert between them now, might as well reuse the logic.

Mostly for the various specializations it does, but might also save some monomorphization work if, say, people collect slice iterators into both `Vec`s and `VecDeque`s.

Author: bors