Make closures carry their own ClosureKind, rather than deducing what it is from movability

compiler/rustc_hir_pretty/src/lib.rs

@@ -1407,7 +1407,7 @@ impl<'a> State<'a> {
                 body,
                 fn_decl_span: _,
                 fn_arg_span: _,
-                movability: _,
+                kind: _,
                 def_id: _,
             }) => {
                 self.print_closure_binder(binder, bound_generic_params);