Bug 27200: (follow-up) Browse search interface update

Bug 27200: (follow-up) Browse search interface update

This patch updates the browse search interface to confirm to new
interface patterns in the Bootstrap 4 framework, especially in the form
markup.

The results list has been changed to a Bootstrap "Collapse" component
configured as an accordion
(https://getbootstrap.com/docs/4.5/components/collapse/#accordion-example).

Instead of loading the bibliographic record results below the list of
terms returned, the bibliographic results are now displayed in the
"panel" expanded below the selected term. Subtitle has been added to the
information displayed about the bibliographic record.

To test you must be using ElasticSearch and the OpacBrowseSearch
preference must be enabled. Apply the patch and rebuild the OPAC CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

- Open the "Browse search" page in the OPAC.
- Test various searches: Author, Subject, and Title.
- When results are found, the should be displayed as a Bootstrap-styled
  accordion widget. Clicking any individual result should expand the
  panel containing the corresponding records.
- Clicking the record link should open the bibliographic detail page in
  a new window.
- When no results are found, a Bootstrap-style "alert" box should
  appear.

Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>