[Library | Explore | new-theme]: Added a container for modals | Fixes in orcid modal | for journals and registries use common query for beta & prod.

1. app.component.ts: Added <div id="modal-container"></div>.
2. alert.ts: [Bug fix] Updated target container in modal to id #modal-container (get portal specific css and have a generic z-index).
3. datasourcesHelper.class.ts: In method getQueryPrefix(), have a common setting for beta & prod environments.
4. orcid-work.component.ts: In grant modal, removed uk-text-center class and added [overflowBody]=false.

library-css/landing-utils.css

@@ -378,6 +378,7 @@
   z-index: 981;
 }
 
+/* Remove the following rule when .less is used for openaire theme */
 .landing .uk-offcanvas .uk-dropdown {
   left: auto !important;
   right: auto !important;