Add show more/less toggle for entire threads in web UI (#6733)

app/javascript/mastodon/actions/statuses.js

app/javascript/mastodon/components/column_header.js

app/javascript/mastodon/components/status.js

app/javascript/mastodon/containers/status_container.js

...pt/mastodon/features/status/components/detailed_status.js

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

app/javascript/mastodon/reducers/statuses.js

app/javascript/styles/mastodon/components.scss