[Feature Request] el-select Remote retrieve the return value is not the default does not display the custom option

### Existing Component
Yes

### Component Name
el-select

### Description
use el-select component remote search data and set properties 'allow-create',default does not display the custom option，Or to a custom option plus some suffixes, through the slot in the form of；Please as soon as possible to solve this problem, from the other side of the Atlantic Christopher qiqi eagerly looking forward to your reply