[Bug Report] tooltip content too long and position cause tooltip beyond screen width

### Element UI version
2.11.1

### OS/Browsers version
macOS 10.13.6 / chrome 79.0.3928.4

### Vue version
2.6.10

### Reproduction Link
https://jsfiddle.net/1a6t47Lb/7/

### Steps to reproduce
move mouse over the 'show tooltip' which has the style 'text-align:right' div the tooltip show but its position style is 'left: -12px' cause the tooltip content oversize the screen width. the same issue happened when the table column add show-overflow-tooltip property

### What is Expected?
the tooltip should show all content and not oversize the screen width

### What is actually happening?
the tooltip content oversize the screen width and its style "left: -12px"