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

compiler/rustc_hir/src/intravisit.rs

@@ -757,7 +757,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
             capture_clause: _,
             fn_decl_span: _,
             fn_arg_span: _,
-            movability: _,
+            kind: _,
             constness: _,
         }) => {
             walk_list!(visitor, visit_generic_param, bound_generic_params);