MDL-74280 reportbuilder: ensure calendar panel zIndex calculated.

Since 29c00fc1 it is calculated dynamically. Ensure all elements
that would otherwise overlap the panel add appropriate class so
they are accounted for during this calculation.

lib/templates/dynamic_tabs.mustache

@@ -46,7 +46,7 @@
 
 <div class="dynamictabs">
     {{#showtabsnavigation}}
-        <ul class="nav nav-tabs mb-4" id="dynamictabs-tabs" role="tablist">
+        <ul class="nav nav-tabs mb-4 moodle-has-zindex" id="dynamictabs-tabs" role="tablist">
             {{#tabs}}
                 <li class="nav-item" role="presentation">
                     <a class="nav-link {{#active}}active{{/active}} {{^enabled}}disabled{{/enabled}}" id="{{shortname}}-tab" data-toggle="tab" href="#{{shortname}}" role="tab" aria-controls="{{shortname}}">

reportbuilder/templates/local/filters/area.mustache

@@ -37,7 +37,7 @@
     </span>
 </button>
 {{! Filters content }}
-<div class="filters-dropdown dropdown-menu dropdown-menu-right" aria-labelledby="dropdownFiltersButton">
+<div class="filters-dropdown dropdown-menu dropdown-menu-right moodle-has-zindex" aria-labelledby="dropdownFiltersButton">
     <div id="filters" class="reportbuilder-filters-sidebar" data-region="report-filters">
         <div class="p-3">
             {{#filtersform}}