[GH-5915] Clicking on @mention of a user in a post shows the profile popover (#6129)

* post message at-mention profile pop-over

* remove hover effect to special mentions

* make non-clickable the non-existing at-mention username

* fix "video call" position

* use usernameMap instead of initially defined liteUsernameMap

* update per comments

webapp/components/rhs_comment.jsx

@@ -1,11 +1,11 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See License.txt for license information.
 
-import UserProfile from './user_profile.jsx';
+import UserProfile from './profile_popover/username_profile_popover.jsx';
 import FileAttachmentListContainer from './file_attachment_list_container.jsx';
 import PendingPostOptions from 'components/post_view/components/pending_post_options.jsx';
 import PostMessageContainer from 'components/post_view/components/post_message_container.jsx';
-import ProfilePicture from 'components/profile_picture.jsx';
+import ProfilePicture from 'components/profile_popover/picture_profile_popover.jsx';
 import ReactionListContainer from 'components/post_view/components/reaction_list_container.jsx';
 import RhsDropdown from 'components/rhs_dropdown.jsx';