Remove Hash and Eq from AstNodeRef for types not implementing Eq or Hash (#16100)

## Summary

This is a follow up to
https://github.com/astral-sh/ruff/pull/15763#discussion_r1949681336

It reverts the change to using ptr equality for `AstNodeRef`s, which in
turn removes the `Eq`, `PartialEq`, and `Hash` implementations for
`AstNodeRef`s parametrized with AST nodes.
Cheap comparisons shouldn't be needed because the node field is
generally marked as `[#tracked]` and `#[no_eq]` and removing the
implementations even enforces that those
attributes are set on all `AstNodeRef` fields (which is good).

The only downside this has is that we technically wouldn't have to mark
the `Unpack::target` as `#[tracked]` because
the `target` field is accessed in every query accepting `Unpack` as an
argument.

Overall, enforcing the use of `#[tracked]` seems like a good trade off,
espacially considering that it's very likely that
we'd probably forget to mark the `Unpack::target` field as tracked if we
add a new `Unpack` query that doesn't access the target.

## Test Plan

`cargo test`

crates/red_knot_python_semantic/src/unpack.rs

@@ -36,6 +36,7 @@ pub(crate) struct Unpack<'db> {
     /// expression is `(a, b)`.
     #[no_eq]
     #[return_ref]
+    #[tracked]
     pub(crate) target: AstNodeRef<ast::Expr>,
 
     /// The ingredient representing the value expression of the unpacking. For example, in