Merge branch '212487-suggest-pipeline-popover-should-slide-behind-nav-bar' into 'master'

Resolve "Suggest pipeline popover should slide behind nav bar"

Closes #212487

See merge request gitlab-org/gitlab!28039

app/assets/stylesheets/framework/header.scss

 .navbar-gitlab {
   padding: 0 16px;
-  z-index: 1000;
+  z-index: $header-zindex;
   margin-bottom: 0;
   min-height: $header-height;
   border: 0;

app/assets/stylesheets/framework/variables.scss

@@ -418,6 +418,7 @@ $browser-scrollbar-size: 10px;
  * Misc
  */
 $header-height: 40px;
+$header-zindex: 1000;
 $suggestion-header-height: 46px;
 $ide-statusbar-height: 25px;
 $fixed-layout-width: 1280px;

app/assets/stylesheets/pages/editor.scss

@@ -221,3 +221,7 @@
 .editor-title-row {
   margin-bottom: 20px;
 }
+
+.popover.suggest-gitlab-ci-yml {
+  z-index: $header-zindex - 1;
+}