Bug 37748: In Bootstrap 5 "disabled" class must be on anchor tag, not list item

Bug 37748: In Bootstrap 5 "disabled" class must be on anchor tag, not list item

This patch revises the markup for disabled dropdown menu items to
conform to Bootstrap 5 requirements. The patch also revises many
instances of Bootstrap tooltips which were not working -- tooltips which
should be shown with many of the disable dropdown items.

In BS5, a tooltip can't be attached to a disabled link. Instead the
tooltip must be attached to the link's container. These changes also
include the addition of "aria-disabled='true'" to the disabled menu
items.

Sponsored-by: Athens County Public Libraries
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>