refactor(runtime-core): refactor slots resolution

Get rid of need for setup proxy in production mode and improve console
inspection in dev mode

packages/runtime-core/src/vnode.ts

@@ -438,7 +438,9 @@ export function normalizeChildren(vnode: VNode, children: unknown) {
       return
     } else {
       type = ShapeFlags.SLOTS_CHILDREN
-      if (!(children as RawSlots)._) {
+      if (!(children as RawSlots)._ && !(InternalObjectSymbol in children!)) {
+        // if slots are not normalized, attach context instance
+        // (compiled / normalized slots already have context)
         ;(children as RawSlots)._ctx = currentRenderingInstance
       }
     }