Bug 32003: Add page-section to order search results and fix heading hierarchy

Bug 32003: Add page-section to order search results and fix heading hierarchy

This adds a page-section to the order search results and moves
the former second h1 heading 'search results' to a h2 heading
below 'Order search', so we have a proper hierarchy

In acquisitions:
* Make sure you have an order with at least one order line
* Do an empty orders search
* Verify there are 2 h1 headings on the page and the results table doesn't
  have a white background
* Apply patch
* Verify the results list now has a white background and the second
  now smaller heading has been moved into this area

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>