Rollup merge of #90427 - jkugelman:must-use-alloc-leak, r=joshtriplett

Add #[must_use] to alloc functions that would leak memory

As [requested](https://github.com/rust-lang/rust/pull/89899#issuecomment-955600779) by `@joshtriplett.`

> Please do go ahead and add the ones whose only legitimate use for ignoring the return value is leaking memory. (In a separate PR please.) I think it's sufficiently error-prone to call something like alloc and ignore the result that it's legitimate to require `let _ =` for that.

I added `realloc` myself. Clippy ignored it because of its `mut` argument.

```rust
alloc/src/alloc.rs:123:1   alloc   unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8;
```

Parent issue: #89692

r? `@joshtriplett`

0 files changed, 0 insertions, 0 deletions