Followup 203f93bcaf
This commit makes sure the background for all the admin
site settings filters (including the filter input and
override checkbox) is consistent no matter what the theme,
as it currently changes based on theme.
This was fixed previously but must have regressed, we
are showing a darker grey background around the
"Only show overridden" checkbox for our Settings tab
in config pages.
* Fixes big gap at the left of the plugins list.
* Fixes plugin settings list padding, the yellow overridden
dot was cut off on mobile.
* Also increased settings filter input size and settings
sidebar button margin.
