Auto merge of #120100 - oli-obk:astconv_lifetimes, r=BoxyUwU

Don't forget that the lifetime on hir types is `'tcx`

This PR just tracks the `'tcx` lifetime to wherever the original objects actually have that lifetime. This code is needed for https://github.com/rust-lang/rust/pull/107606 (now #120131) so that `ast_ty_to_ty` can invoke `lit_to_const` on an argument passed to it. Currently the argument is `&hir::Ty<'_>`, but after this PR it is `&'tcx hir::Ty<'tcx>`.

compiler/rustc_hir/src/hir.rs

@@ -248,7 +248,7 @@ pub struct InferArg {
 }
 
 impl InferArg {
-    pub fn to_ty(&self) -> Ty<'_> {
+    pub fn to_ty(&self) -> Ty<'static> {
         Ty { kind: TyKind::Infer, span: self.span, hir_id: self.hir_id }
     }
 }