For screens wider than 2300px, show 4 colums of search results, as 3 columns looked quite stretched out.
This change also increases the default number of search results from 30 to 36, so that the columns have an even number of results, regardless of whether there are 2, 3, or 4 of them.
Props nielslange.
Fixes#43573.
Built from https://develop.svn.wordpress.org/trunk@43669
git-svn-id: http://core.svn.wordpress.org/trunk@43498 1a063a9b-81f0-0310-95a4-ce76da25c4cd
8617817fb4