[A11Y] Change color of the Views hidden fields for the Seven theme

Description of the need

Backdrop adds a [hidden] nomenclature to the end of a hidden field, however it still gets lost in the mix if there are a lot of fields, and the field names are long and wrap.

Example vs

Proposed solution

The proposed resolution is to change the color of the hidden items for better legibility between hidden and shown fields. I also recommend italicizing the hidden fields.

Example of real-world change on a Drupal site:

Additional information

The color used in my example is: rgb(114,131,145)

Recommended CSS addition (with slightly updated color recommendation):

Files to be changed for CSS: * core/modules/views_ui/css/views_ui.admin.theme.css

Files to be changed for moving [hidden] to the front of the line: * core/modules/views_ui/views_ui.admin.inc

.views-edit-view .views-field-excluded {
  color: rgb(160 160 160);
  font-style: italic;
}

Draft of feature description for Press Release (1 paragraph at most)

The Backdrop Seven theme now changes the color of hidden fields to better show which fields are hidden vs shown.