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: https://github.com/rust-lang/rust/pull/99696#pullrequestreview-1134072751

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

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -828,7 +828,7 @@ where
                 } else {
                     match variables.probe(vid) {
                         TypeVariableValue::Known { value: u } => {
-                            drop(variables);
+                            drop(inner);
                             self.relate(u, u)
                         }
                         TypeVariableValue::Unknown { universe: _universe } => {