Auto merge of #111530 - Urgau:uplift_undropped_manually_drops, r=comp…

…iler-errors

Uplift `clippy::undropped_manually_drops` lint

This PR aims at uplifting the `clippy::undropped_manually_drops` lint.

## `undropped_manually_drops`

(warn-by-default)

The `undropped_manually_drops` lint check for calls to `std::mem::drop` with a value of `std::mem::ManuallyDrop` which doesn't drop.

### Example

```rust
struct S;
drop(std::mem::ManuallyDrop::new(S));
```

### Explanation

`ManuallyDrop` does not drop it's inner value so calling `std::mem::drop` will not drop the inner value of the `ManuallyDrop` either.

-----

Mostly followed the instructions for uplifting an clippy lint described here: rust-lang/rust#99696 (review)

`@rustbot` label: +I-lang-nominated
r? compiler

-----

For Clippy:

changelog: Moves: Uplifted `clippy::undropped_manually_drops` into rustc

core/tests/manually_drop.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(not(bootstrap), allow(undropped_manually_drops))]
+
 use core::mem::ManuallyDrop;
 
 #[test]