[AC-2436] Show unassigned items banner in web (#8655)

* Boostrap basic banner, show for all admins

* Remove UI banner, fix method calls

* Invert showBanner -> hideBanner

* Add api call

* Minor tweaks and wording

* Change to active user state

* Add tests

* Fix mixed up names

* Simplify logic

* Add feature flag

* Do not clear on logout

* Update apps/web/src/locales/en/messages.json

---------

Co-authored-by: Addison Beck <github@addisonbeck.com>

apps/web/src/app/layouts/header/web-header.component.html

@@ -1,16 +1,18 @@
 <bit-banner
   class="-tw-m-6 tw-flex tw-flex-col tw-pb-6"
-  (onClose)="webLayoutMigrationBannerService.hideBanner()"
-  *ngIf="webLayoutMigrationBannerService.showBanner$ | async"
+  (onClose)="webUnassignedItemsBannerService.hideBanner()"
+  *ngIf="
+    (unassignedItemsBannerEnabled$ | async) && (webUnassignedItemsBannerService.showBanner$ | async)
+  "
 >
-  {{ "newWebApp" | i18n }}
+  {{ "unassignedItemsBanner" | i18n }}
   <a
-    href="https://bitwarden.com/blog/bitwarden-design-updating-the-navigation-in-the-web-app"
+    href="https://bitwarden.com/help/unassigned-vault-items-moved-to-admin-console"
     bitLink
     linkType="contrast"
     target="_blank"
     rel="noreferrer"
-    >{{ "releaseBlog" | i18n }}</a
+    >{{ "learnMore" | i18n }}</a
   >
 </bit-banner>
 <header