Change featured hashtags to be displayed in navigation panel (#19382)

app/javascript/mastodon/components/hashtag.js

app/javascript/mastodon/components/navigation_portal.js

...ipt/mastodon/features/account/components/featured_tags.js

...on/features/account/containers/featured_tags_container.js

app/javascript/mastodon/features/account/navigation.js

...t/mastodon/features/account_timeline/components/header.js

...cript/mastodon/features/ui/components/navigation_panel.js

app/javascript/styles/mastodon/components.scss

app/serializers/rest/featured_tag_serializer.rb