[Feature Request] Can el-col support auto-layout columns (auto sizing)?

### Existing Component
Yes

### Component Name
el-col

### Description
Would it be possible to add support for el-col to...

- support 'auto' column size, where the size of the column matches the natural size of the content (wraps content)
- support setting no explicit column size, in which case the column fills the remaining available space of the row.

Both requests can be achieved by mainly tweaking the flexbox css styling of columns.
The requested options are available in Bootstrap too, and are briljant tools when creating layouts (see https://getbootstrap.com/docs/4.4/layout/grid/#auto-layout-columns for some examples)