Enhanced doucmentation of binary search methods for `slice` and `VecDeque` for unsorted instances
Fixes#106746. Issue #106746 raises the concern that the binary search methods for slices and deques aren't explicit enough about the fact that they are only applicable to sorted slices/deques. I changed the explanation for these methods. I took the relatively harsh description of the behaviour of binary search on unsorted collections ("unspecified and meaningless") from the description of the [`partition_point`](https://doc.rust-lang.org/std/primitive.slice.html#method.partition_point) method:
> If this slice is not partitioned, the returned result is unspecified and meaningless, as this method performs a kind of binary search.
d6f27401f1