Hover background on lists
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### Description
When I open gitlab with fluid interface on big screen (2560x1440) lists on many pages are very wide. That won't be much problem if there would be some background on hover highlighting hovered row. Right now I'm not always sure which branch I'm deleting because name of a branch is to far away to buttons.
### Proposal
Add background highlight on hover to rows on lists (branches, issues, labels, etc)
### Links / references
issue