Rollup merge of rust-lang#134536 - Urgau:fn-ptr-option, r=compiler-errors,traviscross

Lint on fn pointers comparisons in external macros

This PR extends the recently stabilized `unpredictable_function_pointer_comparisons` lint ~~to also lint on `Option<{function pointer}>` and~~ as well as linting in external macros (as to catch `assert_eq!` and others).

```rust
assert_eq!(Some::<FnPtr>(func), Some(func as unsafe extern "C" fn()));
//~^ WARN function pointer comparisons

#[derive(PartialEq, Eq)]
struct A {
    f: fn(),
    //~^ WARN function pointer comparisons
}
```

Fixes rust-lang#134527

Author: matthiaskrgr

core/src/task/wake.rs

@@ -104,6 +104,7 @@ impl RawWaker {
 /// synchronization. This is because [`LocalWaker`] is not thread safe itself, so it cannot
 /// be sent across threads.
 #[stable(feature = "futures_api", since = "1.36.0")]
+#[allow(unpredictable_function_pointer_comparisons)]
 #[derive(PartialEq, Copy, Clone, Debug)]
 pub struct RawWakerVTable {
     /// This function will be called when the [`RawWaker`] gets cloned, e.g. when