Rollup merge of #55837 - Centril:spökdata-skall-vara-strukturellt-matchbar, r=eddyb

Rollup merge of #55837 - Centril:spökdata-skall-vara-strukturellt-matchbar, r=eddyb

Make PhantomData #[structural_match]

fixes https://github.com/rust-lang/rust/issues/55028

This makes `PhantomData<T>` structurally matchable, irrespective of whether `T` is, per the discussion on this week's language team meeting (the general consensus was that this was a bug-fix).

All types containing `PhantomData<T>` and which used `#[derive(PartialEq, Eq)]` and were previously not `#[structural_match]` only because of `PhantomData<T>` will now be `#[structural_match]`.

r? @nikomatsakis