[Bug Report] Tooltip, component in slot cannot access vuex store

### Element UI version
2.13.2

### OS/Browsers version
MacOS

### Vue version
2.6.11

### Reproduction Link
https://codesandbox.io/s/element-ui-repro-zfyyo?file=/src/components/Inside.vue

### Steps to reproduce
There is component named Inside.vue which is called from HelloWorld.vue

HelloWorld.vue has element UI tooltip component and slot is filled using Inside.vue component

### What is Expected?
context.root.$store is defined on both of HelloWorld.vue and Inside.vue

### What is actually happening?
HelloWorld.vue has context.root.$store defined but none on Inside.vue