[Feature Request] the el-upload component to add a file replacement feature

### Existing Component
是

### Component Name
el-upload

### Description
Now the el-upload component, after uploading a file, if you want to modify it, you can only delete it and upload it again. I hope to add a replacement function, which can directly select the file upload and replace the uploaded file, especially when the uploaded file is a picture and multiple files, it is more convenient