[GH-25022]: Add Academy links to Teams training (#25150)

* feat: add link to teams dropdown menu

* fix: refactor link to separate component and update styles

* feat: add academy link to team's join page and settings modal

* fix: i18n and update test snapshots

* fix link styles & update test snapshot

* add state for unit tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Scott Bishel <scott.bishel@mattermost.com>

webapp/channels/src/plugins/test/__snapshots__/main_menu_action.test.tsx.snap

@@ -631,6 +631,13 @@ exports[`plugins/MainMenuActions should match snapshot in web view 1`] = `
           to="/create_team"
         />
       </Connect(SystemPermissionGate)>
+      <Memo(MenuGroup)>
+        <div
+          className="MainMenu_dropdown-link"
+        >
+          <LearnAboutTeamsLink />
+        </div>
+      </Memo(MenuGroup)>
     </Memo(MenuGroup)>
     <Memo(MenuGroup)>
       <MenuItemAction