Auto merge of #120006 - cjgillot:no-hir-owner, r=wesleywiser

Get rid of the hir_owner query.

This query was meant as a firewall between `hir_owner_nodes` which is supposed to change often, and the queries that only depend on the item signature. That firewall was inefficient, leaking the contents of the HIR body through `HirId`s.

`hir_owner` incurs a significant cost, as we need to hash HIR twice in multiple modes. This PR proposes to remove it, and simplify the hashing scheme.

For the future, `def_kind`, `def_span`... are much more efficient for incremental decoupling, and should be preferred.

compiler/rustc_hir/src/hir.rs

@@ -841,7 +841,7 @@ pub struct OwnerNodes<'tcx> {
 }
 
 impl<'tcx> OwnerNodes<'tcx> {
-    fn node(&self) -> OwnerNode<'tcx> {
+    pub fn node(&self) -> OwnerNode<'tcx> {
         use rustc_index::Idx;
         let node = self.nodes[ItemLocalId::new(0)].as_ref().unwrap().node;
         let node = node.as_owner().unwrap(); // Indexing must ensure it is an OwnerNode.
@@ -1305,7 +1305,7 @@ pub enum UnsafeSource {
     UserProvided,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)]
 pub struct BodyId {
     pub hir_id: HirId,
 }