refactor(compiler-core): use more concise marker for compiled slots

packages/runtime-core/src/componentSlots.ts

@@ -23,7 +23,7 @@ export type RawSlots = {
   // manual render fn hint to skip forced children updates
   $stable?: boolean
   // internal, indicates compiler generated slots = can skip normalization
-  _compiled?: boolean
+  _?: 1
 }
 
 const normalizeSlotValue = (value: unknown): VNode[] =>
@@ -51,7 +51,7 @@ export function resolveSlots(
   let slots: InternalSlots | void
   if (instance.vnode.shapeFlag & ShapeFlags.SLOTS_CHILDREN) {
     const rawSlots = children as RawSlots
-    if (rawSlots._compiled) {
+    if (rawSlots._ === 1) {
       // pre-normalized slots object generated by compiler
       slots = children as Slots
     } else {