Rollup merge of rust-lang#105120 - solid-rs:patch/kmc-solid/maintainance, r=thomcc

kmc-solid: `std::sys` code maintenance

Includes a set of changes to fix the [`*-kmc-solid_*`](https://doc.rust-lang.org/nightly/rustc/platform-support/kmc-solid.html) Tier 3 targets and make some other improvements.

- Address `fuzzy_provenance_casts` by using `expose_addr` and `from_exposed_addr` for pointer-integer casts
- Add a stub implementation of `is_terminal` (rust-lang#98070)
- Address `unused_imports` and `unused_unsafe`
- Stop doing `Box::from_raw(&*(x: Box<T>) as *const T as *mut T)`

Author: matthiaskrgr