Add `limited` attribute to accounts in REST API and a warning in web UI (#18344)

app/javascript/mastodon/actions/accounts.js

app/javascript/mastodon/components/avatar.js

...javascript/mastodon/features/account/components/header.js

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

...tures/account_timeline/components/limited_account_hint.js

.../features/account_timeline/containers/header_container.js

app/javascript/mastodon/features/account_timeline/index.js

app/javascript/mastodon/features/followers/index.js

app/javascript/mastodon/features/following/index.js

app/javascript/mastodon/reducers/accounts.js

app/javascript/mastodon/selectors/index.js

app/javascript/styles/mastodon/components.scss

app/serializers/rest/account_serializer.rb