Bug 35037: Revise the appearance of the last patron button

Bug 35037: Revise the appearance of the last patron button

Following Bug 21246 I find the button to be too obtrusive. This patch
makes CSS changes to the style of the "Last patron" button shown in the
staff interface when the "showLastPatron" system preference is enabled.

To test, apply the patch and rebuild the staff interface CSS.

- Enable the showLastPatron system preference if necessary.
- Go to Circulation in the staff interface and check out to a patron.
- A "Last patron" button should appear on the right-hand end of the
  breadcrumbs bar.
- Check that the link, dropdown button, and dropdown menu look good.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>