refactor: adjust component options merge cache strategy

BREAKING CHANGE: optionMergeStrategies functions no longer receive
the component instance as the 3rd argument. The argument was technically
internal in Vue 2 and only used for generating warnings, and should not
be needed in userland code. This removal enables much more efficient
caching of option merging.

packages/runtime-core/src/compat/instance.ts

@@ -35,7 +35,6 @@ import {
   legacyresolveScopedSlots
 } from './renderHelpers'
 import { resolveFilter } from '../helpers/resolveAssets'
-import { resolveMergedOptions } from '../componentOptions'
 import { InternalSlots, Slots } from '../componentSlots'
 import { ContextualRenderFn } from '../componentRenderContext'
 
@@ -128,16 +127,6 @@ export function installCompatInstanceProperties(map: PublicPropertiesMap) {
       // needed by many libs / render fns
       $vnode: i => i.vnode,
 
-      // inject addtional properties into $options for compat
-      // e.g. vuex needs this.$options.parent
-      $options: i => {
-        let res = resolveMergedOptions(i)
-        if (res === i.type) res = i.type.__merged = extend({}, res)
-        res.parent = i.proxy!.$parent
-        res.propsData = i.vnode.props
-        return res
-      },
-
       // some private properties that are likely accessed...
       _self: i => i.proxy,
       _uid: i => i.uid,