Ability to specify that a list table column is "primary"
|Reported by:||helen||Owned by:||stephdau|
List tables have a "primary" column of sorts; that is, the one with the row actions. We should be able to specify which column is the primary one via API, apply an appropriate class, and display the row actions in cells in that column. Currently, developers customizing the list table columns often need to re-create row actions if they do not use the post name column, or just live with the row actions appearing in a less sensible spot.
This thought stems from three things in particular:
- The above customization example.
- Old experiments (nearly exactly 2 years ago) in making list tables responsive: http://cl.ly/3F1L0N3z1M0F0Z3t0X3W in #18198.
- The assortment of selectors in  that are not particularly robust and not easily reused by developers. We should be able to target something like .has-row-actions instead.