Auto merge of #109732 - Urgau:uplift_drop_forget_ref_lints, r=davidtwco

Uplift `clippy::{drop,forget}_{ref,copy}` lints

This PR aims at uplifting the `clippy::drop_ref`, `clippy::drop_copy`, `clippy::forget_ref` and `clippy::forget_copy` lints.

Those lints are/were declared in the correctness category of clippy because they lint on useless and most probably is not what the developer wanted.

## `drop_ref` and `forget_ref`

The `drop_ref` and `forget_ref` lint checks for calls to `std::mem::drop` or `std::mem::forget` with a reference instead of an owned value.

### Example

```rust
let mut lock_guard = mutex.lock();
std::mem::drop(&lock_guard) // Should have been drop(lock_guard), mutex
// still locked
operation_that_requires_mutex_to_be_unlocked();
```

### Explanation

Calling `drop` or `forget` on a reference will only drop the reference itself, which is a no-op. It will not call the `drop` or `forget` method on the underlying referenced value, which is likely what was intended.

## `drop_copy` and `forget_copy`

The `drop_copy` and `forget_copy` lint checks for calls to `std::mem::forget` or `std::mem::drop` with a value that derives the Copy trait.

### Example

```rust
let x: i32 = 42; // i32 implements Copy
std::mem::forget(x) // A copy of x is passed to the function, leaving the
                    // original unaffected
```

### Explanation

Calling `std::mem::forget` [does nothing for types that implement Copy](https://doc.rust-lang.org/std/mem/fn.drop.html) since the value will be copied and moved into the function on invocation.

-----

Followed the instructions for uplift a clippy describe here: rust-lang/rust#99696 (review)

cc `@m-ou-se` (as T-libs-api leader because the uplifting was discussed in a recent meeting)

Author: bors

tests/fail/stacked_borrows/illegal_write2.rs

@@ -1,3 +1,5 @@
+#![allow(drop_ref)]
+
 fn main() {
     let target = &mut 42;
     let target2 = target as *mut _;

tests/fail/uninit_buffer.rs

@@ -1,5 +1,7 @@
 //@error-in-other-file: memory is uninitialized at [0x4..0x10]
 
+#![allow(drop_copy)]
+
 use std::alloc::{alloc, dealloc, Layout};
 use std::slice::from_raw_parts;
 

tests/fail/uninit_buffer_with_provenance.rs

@@ -2,6 +2,8 @@
 //@normalize-stderr-test: "a[0-9]+" -> "ALLOC"
 #![feature(strict_provenance)]
 
+#![allow(drop_copy)]
+
 // Test printing allocations that contain single-byte provenance.
 
 use std::alloc::{alloc, dealloc, Layout};

tests/pass/stacked-borrows/zst-field-retagging-terminates.rs

@@ -1,5 +1,8 @@
 //@compile-flags: -Zmiri-retag-fields
 // Checks that the test does not run forever (which relies on a fast path).
+
+#![allow(drop_copy)]
+
 fn main() {
     let array = [(); usize::MAX];
     drop(array); // Pass the array to a function, retagging its fields