Rollup merge of #143554 - okaneco:const_slice_rotate, r=Amanieu,tgross35

slice: Mark `rotate_left`, `rotate_right` unstably const

Tracking issue rust-lang/rust#143812

- Add the const unstable `const_slice_rotate` feature
- Mark `<[T]>::rotate_left` and `<[T]>::rotate_right` as const unstable

The internal rotate functions use [`<*mut T>::replace`](https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.replace) and [`ptr::swap_nonoverlapping`](https://doc.rust-lang.org/stable/core/ptr/fn.swap_nonoverlapping.html) which were const-stabilized in 1.88.

Two changes were needed in the `rotate.rs` module to make these functions const:
1. A usage of `cmp::min` was replaced with a local function implementation of [`Ord::min`](https://doc.rust-lang.org/1.88.0/src/core/cmp.rs.html#1048-1053).
2. A `for start in 1..gcd` loop was changed to a while loop with an increment variable.

This needs libs-api approval and cc-ing const-eval.

Author: matthiaskrgr