Additional tweaks for bootstrap5 support

btn-default -> btn-secondary
use mb-3 to add margin to bottom of input-groups
use $.modal('show') to show modals
use bi bi-trash icon (font-awesome doesn't seem to be included with bs5
data-bs-dismiss on the modal close buttons
put recheck templates in container divs
add input-group-text class to addon icons for input fields

mfa/templates/U2F/recheck.html

@@ -24,7 +24,7 @@
           </div>
 
           <div class="row">
-          <div style="padding-left: 15px">
+          <div class="col-md-12 mb-3" style="padding-left: 15px">
 
             {% if request.session.mfa_methods|length > 1 %}
                 <a href="{%  url 'mfa_methods_list' %}">Select Another Method</a>